Method of and system for producing images of objects using planar laser illumination beams and image detection arrays

ABSTRACT

Methods of and systems for illuminating objects using planar laser illumination beams having substantially-planar spatial distribution characteristics that extend through the field of view (FOV) of image formation and detection modules employed in such systems. Each planar laser illumination beam is produced from a planar laser illumination beam array (PLIA) comprising an plurality of planar laser illumination modules (PLIMs). Each PLIM comprises a visible laser diode (VLD, a focusing lens, and a cylindrical optical element arranged therewith. The individual planar laser illumination beam components produced from each PLIM are optically combined to produce a composite substantially planar laser illumination beam having substantially uniform power density characteristics over the entire spatial extend thereof and thus the working range of the system. Preferably, each planar laser illumination beam component is focused so that the minimum beam width thereof occurs at a point or plane which is the farthest or maximum object distance at which the system is designed to acquire images, thereby compensating for decreases in the power density of the incident planar laser illumination beam due to the fact that the width of the planar laser illumination beam increases in length for increasing object distances away from the imaging optics. By virtue of the present invention, it is now possible to use both VLDs and high-speed CCD-type image detectors in conveyor, hand-held and hold-under type scanning applications alike, enjoying the advantages and benefits that each such technology has to offer, while avoiding the shortcomings and drawbacks hitherto associated therewith.

CROSS-REFERENCE TO RELATED U.S. APPLICATIONS

[0001] This is a Continuation-in-Part of copending application Ser. No.______ entitled “Method Of And System For Producing Images Of ObjectsUsing Planar Laser Illumination Beams And Image Detection Arrays” filedNov. 24, 2000 under 37 C.F.R. 1.10 (Express Mail No. EL701906400US);International Application PCT/US99/06505 filed Mar. 24, 1999, publishedas WIPO WO 99/49411; International Application PCT/US99/28530 filed Dec.2, 1999, published as WIPO Publication WO 00/33239; copendingapplication Ser. No. 09/452,976 filed Dec. 2, 1999; application Ser. No.09/327,756 filed Jun. 7, 1999, which is a Continuation-in-Part ofapplication Ser. No. 09/305,896 filed May 5, 1999, which is aContinuation-in-Part of copending application Ser. No. 09/275,518 filedMar. 24, 1999, which is a Continuation-in-Part of copending applicationSer. No. 09/274,265 filed Mar. 22, 1999; Ser. No. 09/243,078 filed Feb.2, 1999; Ser. No. 09/241,930 filed Feb. 2, 1999; Ser. No. 09/157,778filed Sep. 21, 1998; Ser. No. 09/047,146 filed Mar. 24, 1998, Ser. No.08/949,915 filed Oct. 14, 1997, now U.S. Pat. No. 6,158,659; Ser. No.08/854,832 filed May 12, 1997, now U.S. Pat. No. 6,085,978; Ser. No.08/886,806 filed Apr. 22, 1997, now U.S. Pat. No. 5,984,185; Ser. No.08/726,522 filed Oct. 7, 1996, now U.S. Pat. No. 6,073,846; Ser. No.08/573,949 filed Dec. 18, 1995, now abandoned; each said applicationbeing commonly owned by Assignee, Metrologic Instruments, Inc., ofBlackwood, N.J., and incorporated herein by reference as if fully setforth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The present invention relates generally to an improved method ofand system for illuminating the surface of objects during imageformation and detection operations, and also to an improved method ofand system for producing digital images using such improved methods ofobject illumination.

[0004] 2. Brief Description of the Prior Art

[0005] The use of image-based bar code symbol readers and scanners iswell known in the field of auto-identification. Examples of image-basedbar code symbol reading/scanning systems include, for example, hand-handscanners, point-of-sale (POS) scanners, and industrial-type conveyorscanning systems.

[0006] Presently, most commercial image-based bar code symbol readersare constructed using charge-coupled device (CCD) imagesensing/detecting technology. Unlike laser-based scanning technology,CCD imaging technology has particular illumination requirements whichdiffer from application to application.

[0007] Most prior art CCD-based image scanners, employed inconveyor-type package identification systems, require high-pressuresodium, metal halide or halogen lamps and large, heavy and expensiveparabolic or elliptical reflectors to produce sufficient lightintensities to illuminate the large depth of field scanning fieldssupported by such industrial scanning systems. Even when the light fromsuch lamps is collimated or focused using such reflectors, light strikesthe target object other than where the imaging optics of the CCD-basedcamera are viewing. Since only a small fraction of the lamps outputpower is used to illuminate the CCD camera's field of view, the totaloutput power of the lamps must be very high to obtain the illuminationlevels required along the field of view of the CCD camera. The balanceof the output illumination power is simply wasted in the form of heat.

[0008] Most prior art CCD-based hand-held image scanners use an array oflight emitting diodes (LEDs) to flood the field of view of the imagingoptics in such scanning systems. A large percentage of the outputillumination from these LED sources is dispersed to regions other thanthe field of view of the scanning system. Consequently, only a smallpercentage of the illumination is actually collected by the imagingoptics of the system, Examples of prior art CCD hand-held image scannersemploying LED illumination arrangements are disclosed in US Pat. Nos.Re. 36,528, 5,777,314, 5,756,981, 5,627,358, 5,484,994, 5,786,582, and6,123,261 to Roustaei, each assigned to Symbol Technologies, Inc. andincorporated herein by reference in its entirety. In such prior artCCD-based hand-held image scanners, an array of LEDs are mounted in ascanning head in front of a CCD-based image sensor that is provided witha cylindrical lens assembly. The LEDs are arranged at an angularorientation relative to a central axis passing through the scanning headso that a fan of light is emitted through the light transmissionaperture thereof that expands with increasing distance away from theLEDs. The intended purpose of this LED illumination arrangement is toincrease the “angular distance” and “depth of field” of CCD-based barcode symbol readers. However, even with such improvements in LEDillumination techniques, the working distance of such hand-held CCDscanners can only be extended by using more LEDs within the scanninghead of such scanners to produce greater illumination output therefrom,thereby increasing the cost, size and weight of such scanning devices.

[0009] Similarly, prior art “hold-under” and “hands-free presentation”type CCD-based image scanners suffer from shortcomings and drawbackssimilar to those associated with prior art CCD-based hand-held imagescanners.

[0010] Thus, there is a great need in the art for an improved method ofand system for illuminating the surface of objects during imageformation and detection operations, and also an improved method of andsystem for producing digital images using such improved methods objectillumination, while avoiding the shortcomings and drawbacks of prior artillumination, imaging and scanning systems and methodologies.

OBJECTS AND SUMMARY OF THE PRESENT INVENTION

[0011] Accordingly, a primary object of the present invention is toprovide an improved method of and system for illuminating the surface ofobjects during image formation and detection operations and alsoimproved methods of and systems for producing digital images using suchimproved methods object illumination, while avoiding the shortcomingsand drawbacks of prior art systems and methodologies.

[0012] Another object of the present invention is to provide such animproved method of and system for illuminating the surface of objectsusing a linear array of laser light emitting devices configured togetherto produce a substantially planar beam of laser illumination whichextends in substantially the same plane as the field of view of thelinear array of electronic image detection cells of the system, along atleast a portion of its optical path within its working distance,

[0013] Another object of the present invention is to provide such animage producing system, wherein the linear array of electronic imagedetection cells are realized using charge-coupled device (CCD)technology.

[0014] Another object of the present invention is to provide such animproved method of and system for producing digital images of objectsusing a visible laser diode array for producing a planar laserillumination beam for illuminating the surfaces of such objects, andalso an electronic image detection array for detecting laser lightreflected off the illuminated objects during illumination and imagingoperations.

[0015] Another object of the present invention is to provide such animproved method of and system for illuminating the surfaces of object tobe imaged, using an array of planar laser illumination arrays whichemploy VLDs that are smaller, and cheaper, run cooler, draw less power,have longer lifetimes, and require simpler optics (because theirfrequency bandwidths are very small compared to the entire spectrum ofvisible light).

[0016] Another object of the present invention is to provide such animproved method of and system for illuminating the surfaces of objectsto be imaged, wherein the VLD concentrates all of its output power intoa thin laser beam illumination plane which spatially coincides exactlywith the field of view of the imaging optics of the system, so verylittle light energy is wasted.

[0017] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein the workingdistance of the system can be easily extended by simply changing thebeam focusing and imaging optics, and without increasing the outputpower of the visible laser diode (VLD) sources employed therein.

[0018] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein each planar laserillumination beam is focused so that the minimum width thereof (e.g. 0.6mm along its non-spreading direction) occurs at a point or plane whichis the farthest object distance at which the system is designed tocapture images.

[0019] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein a fixed focallength imaging subsystem is employed, and the laser beam focusingtechnique of the present invention helps compensate for decreases in thepower density of the incident planar illumination beam due to the factthat the width of the planar laser illumination beam for increasingdistances away from the imaging subsystem.

[0020] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein a variable focallength (i.e. zoom) imaging subsystem is employed, and the laser beamfocusing technique of the present invention helps compensate for (i)decreases in the power density of the incident illumination beam due tothe fact that the width of the planar laser illumination beam (i.e.beamwidth) along the direction of the beam's planar extent increases forincreasing distances away from the imaging subsystem, and (ii) any 1/r²type losses that would typically occur when using the planar laserillumination beam of the present invention.

[0021] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein scanned objectsneed only be illuminated along a single plane which is coplanar with aplanar section of the field of view of the image formation and detectionmodule being used in the PLIIM system.

[0022] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein low-power,light-weight, high-response, ultra-compact, high-efficiency solid-stateillumination producing devices, such as visible laser diodes (VLDs), areused to selectively illuminate ultra-narrow sections of a target objectduring image formation and detection operations, in contrast withhigh-power, low-response, heavy-weight, bulky, low-efficiency lightingequipment (e.g. sodium vapor lights) required by prior art illuminationand image detection systems.

[0023] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein the planar laserillumination technique of the present invention enables high-speedmodulation of the planar laser illumination beam, and use of simple(i.e. substantially monochromatic) lens designs for substantiallymonochromatic optical illumination and image formation and detectionoperations.

[0024] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein special measuresare undertaken to ensure that (i) a minimum safe distance is maintainedbetween the VLDs in each PLIM and the user's eyes using a light shield,and (ii) the planar laser illumination beam is prevented from directlyscattering into the FOV of the image formation and detection modulewithin the system housing.

[0025] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein the planar laserillumination beam and the field of view of the image formation anddetection module do not overlap on any optical surface within the PLIIMsystem.

[0026] Another object of the present invention is to provide a planarlaser illumination and imaging (PLIIM) system, wherein the planar laserillumination beams are permitted to spatially overlap with the FOV ofthe imaging lens of the PLIIM only outside of the system housing,measured at a particular point beyond the light transmission window,through which the FOV is projected.

[0027] Another object of the present invention is to provide a planarlaser illumination (PLIM) system for use in illuminating objects beingimaged.

[0028] Another object of the present invention is to provide planarlaser illumination and substantially-monochromatic imaging system,wherein the monochromatic imaging module is realized as an array ofelectronic image detection cells (e.g. CCD).

[0029] Another object of the present invention is to provide a planarlaser illumination and substantially-monochromatic imaging system,wherein the planar laser illumination arrays (PLIAs) and the imageformation and detection (IFD) module are mounted in strict opticalalignment on an optical bench such that there is substantially norelative motion, caused by vibration or temperature changes, ispermitted between the imaging lens within the IFD module and theVLD/cylindrical lens assemblies within the PLIAs.

[0030] Another object of the present invention is to provide a planarlaser illumination and substantially-monochromatic imaging system,wherein the imaging module is realized as a photographic image recordingmodule.

[0031] Another object of the present invention is to provide a planarlaser illumination and substantially-monochromatic imaging system,wherein the imaging module is realized as an array of electronic imagedetection cells (e.g. CCD) having short integration time settings forhigh-speed image capture operations.

[0032] Another object of the present invention is to provide a planarlaser illumination and substantially-monochromatic imaging system,wherein a pair of planar laser illumination arrays are mounted about animage formation and detection module having a field of view, so as toproduce a substantially planar laser illumination beam which is coplanarwith the field of view during object illumination and imagingoperations.

[0033] Another object of the present invention is to provide a planarlaser illumination and monochromatic imaging system, wherein an imageformation and detection module projects a field of view through a firstlight transmission aperture formed in the system housing, and a pair ofplanar laser illumination arrays project a pair of planar laserillumination beams through second set of light transmission apertureswhich are optically isolated from the first light transmission apertureto prevent laser beam scattering within the housing of the system.

[0034] Another object of the present invention is to provide a planarlaser illumination and substantially-monochromatic imaging system, theprinciple of Gaussian summation of light intensity distributions isemployed to produce a planar laser illumination beam having a powerdensity across the width the beam which is substantially the same forboth far and near fields of the system.

[0035] Another object of the present invention is to provide method ofand system for illuminating the surfaces of objects during imageformation and detection operations.

[0036] Another object of the present invention is to provide method ofand system for producing digital images of objects using planar laserillumination beams and electronic image detection arrays.

[0037] Another object of the present invention is to provide method ofand system for producing a planar laser illumination beam to illuminatethe surface of objects and electronically detecting light reflected offthe illuminated objects during planar laser beam illuminationoperations.

[0038] Another object of the present invention is to provide hand-heldlaser illuminated image detection and processing device for use inreading bar code symbols and other character strings.

[0039] Another object of the present invention is to provide method ofand system for producing images of objects by focusing a planar laserillumination beam within the field of view of an imaging lens so thatthe minimum width thereof along its non-spreading direction occurs atthe farthest object distance of the imaging lens.

[0040] Another object of the present invention is to provide planarlaser illumination modules for use in electronic imaging systems, andmethods of designing and manufacturing the same.

[0041] Another object of the present invention is to provide planarlaser illumination arrays for use in electronic imaging systems, andmethods of designing and manufacturing the same.

[0042] Another object of the present invention is to provide an unitarypackage dimensioning and identification system contained in a singlehousing of compact construction, wherein a planar laser illumination andmonochromatic imaging (PLIIM) subsystem is integrated with a LaserDoppler Imaging and Profiling (LDIP) subsystem and contained within asingle housing of compact construction.

[0043] Another object of the present invention is to provide such anunitary package dimensioning and identification system, wherein thePLIIM subsystem projects a field of view through a first lighttransmission aperture formed in the system housing, and a pair of planarlaser illumination beams through second and third light transmissionapertures which are optically isolated from the first light transmissionaperture to prevent laser beam scattering within the housing of thesystem, and the LDIP subsystem projects a pair of laser beams atdifferent angles through a fourth light transmission aperture.

[0044] Another object of the present invention is to provide a fullyautomated unitary-type package identification and measuring system (i.e.contained within a single housing or enclosure), wherein a PLIIM-basedscanning subsystem is used to read bar codes on packages passing belowor near the system, while a package dimensioning subsystem is used tocapture information about the package prior to being identified.

[0045] Another object of the present invention is to provide such anautomated package identification and measuring system, wherein LaserDetecting And Ranging (LADAR-based) scanning methods are used to capturetwo-dimensional range data maps of the space above a conveyor beltstructure, and two-dimensional image contour tracing methods are used toextract package dimension data therefrom.

[0046] Another object of the present invention is to provide such aunitary system, wherein the package velocity is automatically computedusing a pair of laser beams projected at different angular projectionsover the conveyor belt.

[0047] Another object of the present invention is to provide such systemin which lasers beams having multiple wavelengths are used to sensepackages having a wide range of reflectivity characteristics.

[0048] Another object of the present invention is to provide improvedimage-based hand-held scanners, body-wearable scanners,presentation-type scanners, and hold-under scanners which embody thePLIIM subsystem of the present invention.

[0049] Another object of the present invention is to provide a PLIMwhich embody an optical technique that effectively destroys the spatialand/or temporal coherence of the laser illumination sources that areused to generate planar laser illumination beams (PLIBs) withinPLIIM-based systems.

[0050] Another object of the present invention is to provide such PLIM,wherein the spatial coherence of the illumination sources is destroyedby creating multiple “virtual” illumination sources that illuminate theobject at different angles, over the photo-integration time period ofthe electronic image detection array used in the IFD module.

[0051] Another object of the present invention is to provide such PLIM,wherein the optical phase difference between the laser illuminationsources employed therein is changed by a sufficiently large amount(typically a fraction of a wavelength), causing the resulting electricfield at the illumination plane to also change significantly over thephoto-integration time period of the image detector, therebysignificantly reducing the speckle noise pattern observed at the imagedetector.

[0052] Another object of the present invention is to provide a unitary(PLIIM-based) package dimensioning and identification system, whereinthe various information signals are generated by the LDIP subsystem, andprovided to the Camera Control (Computer) Subsystem, and wherein theCamera Control Computer generates digital camera control signals whichare provided to the image formation and detection (IFD subsystem (i.e.“camera”) so that the system can carry out its diverse functions in anintegrated manner, including (1) capturing digital images having (i)square pixels (i.e. 1:1 aspect ratio) independent of package height orvelocity, (ii) significantly reduced speckle-noise levels, and (iii)constant image resolution measured in dots per inch (DPI) independent ofpackage height or velocity and without the use of costly telecentricoptics employed by prior art systems, (2) automatic cropping of capturedimages so that only regions of interest reflecting the package orpackage label are transmitted to either a image-processing based 1-D or2-D bar code symbol decoder or an optical character recognition (OCR)image processor, and (3) automatic image lifting operations.

[0053] As will be described in greater detail in the DetailedDescription of the Illustrative Embodiments set forth below, suchobjectives are achieved in novel methods of and systems for illuminatingobjects (e.g. bar coded packages, textual materials, graphical indicia,etc.) using planar laser illumination beams having substantially-planarspatial distribution characteristics that extend through the field ofview (FOV) of image formation and detection modules (e.g. realizedwithin a CCD-type digital electronic camera, or a 35 mm optical-filmphotographic camera) employed in such systems.

[0054] In each illustrative embodiment of the present invention, thesubstantially planar laser illumination beams are preferably producedfrom a planar laser illumination beam array (PLIA) comprising anplurality of planar laser illumination modules (PLIMs). Each PLIMcomprises a visible laser diode (VLD, a focusing lens, and a cylindricaloptical element arranged therewith. The individual planar laserillumination beam components produced from each PLIM are opticallycombined within the PLIA to produce a composite substantially planarlaser illumination beam having substantially uniform power densitycharacteristics over the entire spatial extend thereof and thus theworking range of the system.

[0055] Preferably, each planar laser illumination beam component isfocused so that the minimum beam width thereof occurs at a point orplane which is the farthest or maximum object distance at which thesystem is designed to acquire images. In the case of both fixed andvariable focal length imaging systems, this inventive principle helpscompensate for decreases in the power density of the incident planarlaser illumination beam due to the fact that the width of the planarlaser illumination beam increases in length for increasing objectdistances away from the imaging subsystem.

[0056] By virtue of the novel principles of the present invention, it isnow possible to use both VLDs and high-speed CCD-type image detectors inconveyor, hand-held and hold-under type scanning applications alike,enjoying the advantages and benefits that each such technology has tooffer, while avoiding the shortcomings and drawbacks hitherto associatedtherewith.

[0057] These and other objects of the present invention will becomeapparent hereinafter and in the claims to Invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] For a more complete understanding of the present invention, thefollowing Detailed Description of the Illustrative Embodiment should beread in conjunction with the accompanying Drawings, wherein:

[0059]FIG. 1A is a schematic representation of a first generalizedembodiment of the planar laser illumination and (electronic) imaging(PLIIM) system of the present invention, wherein a pair of planar laserillumination arrays (PLIAs) are mounted on opposite sides of a linear(i.e. 1-dimensional) type image formation and detection module (IFDM)having a fixed focal length imaging lens, a fixed focal distance andfixed field of view, such that the planar illumination array produces astationary (i.e. non-scanned) plane of laser beam illumination which isdisposed substantially coplanar with the field of view of the imageformation and detection module during object illumination and imagedetection operations carried out by the PLIIM system on a moving barcode symbol or other graphical structure;

[0060]FIG. 1B1 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.1A, wherein the field of view of the image formation and detectionmodule is folded in the downwardly imaging direction by the field ofview folding mirror so that both the folded field of view and resultingstationary planar laser illumination beams produced by the planarillumination arrays are arranged in a substantially coplanarrelationship during object illumination and image detection operations,and a planar laser illumination beam (PLIB) micro-oscillation mechanismis used to micro-oscillate each beam component within the compositeplanar laser illumination beam by a relatively small distance withrespect to each detector element in the stationary linear imagedetection array of the PLIIM system, so as to repeatedly illuminate thedetector element from a different point in space and at a differentmoment in time over the photo-integration period of the detectorelement, thereby destroying the spatial and temporal coherence of thelaser illumination beam received at the detector element and reducingthe speckle-noise level produced thereat;

[0061]FIG. 1B2 is a schematic representation of the PLIIM system shownin FIG. 1A, wherein the linear image formation and detection module isshown comprising a linear array of photo-electronic detectors realizedusing CCD technology, each planar laser illumination array is showncomprising an array of planar laser illumination modules, and a planarlaser illumination beam (PLIB) micro-oscillation mechanism is used tomicro-oscillate each beam component within the composite planar laserillumination beam produced by the planar laser illumination array todestroy the spatial coherence of the laser illumination beam received atthe detector element and thereby reduce the speckle-noise level producedthereat;

[0062]FIG. 1C is a schematic representation of a single planar laserillumination module (PLIM) used to construct each planar laserillumination array shown in FIG. 1B, wherein the planar laserillumination beam emanates substantially within a single plane along thedirection of beam propagation towards an object to be opticallyilluminated;

[0063]FIG. 1D is a schematic diagram of the planar laser illuminationmodule of FIG. 1C, shown comprising a visible laser diode (VLD), a lightcollimating lens, and a cylindrical-type lens element configuredtogether to produce a beam of planar laser illumination;

[0064]FIG. 1E1 is a plan view of the VLD, collimating lens andcylindrical lens assembly employed in the planar laser illuminationmodule of FIG. 1C, showing that the focused laser beam from thecollimating lens is directed on the input side of the cylindrical lens,and the output beam produced therefrom is a planar laser illuminationbeam expanded (i.e. spread out) along the plane of propagation;

[0065]FIG. 1E2 is an elevated side view of the VLD, collimating lens andcylindrical lens assembly employed in the planar laser illuminationmodule of FIG. 1C, showing that the laser beam is transmitted throughthe cylindrical lens without expansion in the direction normal to theplane of propagation, but is focused by the collimating lens at a pointresiding within a plane located at the farthest object distancesupported by the PLIIM system;

[0066]FIG. 1F is a block schematic diagram of the PLIIM system shown inFIG. 1A, comprising a pair of planar laser illumination arrays (drivenby a set of VLD driver circuits that can drive the VLDs in a pulsed-modeof operation), a linear-type image formation and detection module, astationary field of view folding mirror, an image frame grabber, animage data buffer, a decode image processor, and a system controller;

[0067]FIG. 1G1 is a schematic representation of an exemplary realizationof the PLIIM system of FIG. 1A, shown comprising a linear imageformation and detection module, a pair of planar laser illuminationarrays, and a field of view (FOV) folding mirror for folding the fixedfield of view of the linear image formation and detection module in adirection that is coplanar with the plane of laser illumination beamsproduced by the planar laser illumination arrays;

[0068]FIG. 1G2 is a plan view schematic representation of the PLIIMsystem, taken along line 1G2-1G2 in FIG. 1G1, showing the spatial extentof the fixed field of view of the linear image formation and detectionmodule in the illustrative embodiment of the present invention;

[0069] FIGS. 1G3A is an elevated end view schematic representation ofthe PLIIM system, taken along line 1G3-1G3 in FIG. 1G1, showing thefixed field of view of the linear image formation and detection modulebeing folded in the downwardly imaging direction by the field of viewfolding mirror, the planar laser illumination beam produced by eachplanar laser illumination module being directed in the imaging directionsuch that both the folded field of view and planar laser illuminationbeams are arranged in a substantially coplanar relationship duringobject illumination and image detection operations, and a planar laserillumination beam (PLIB) micro-oscillation mechanism used tomicro-oscillate each beam component within the composite planar laserillumination beam produced by the planar laser illumination array todestroy the spatial coherence of the laser illumination beam received atthe detector element and thereby reduce the speckle-noise level producedthereat;

[0070]FIG. 1G3B is an elevated end view schematic representation of thePLIIM system as shown in FIG. 1G3A, wherein the planar laserillumination beam (PLIB) micro-oscillation mechanism is shown tomicro-oscillate each beam component within the composite planar laserillumination beam by a relatively small distance with respect to eachdetector element in the stationary linear image detection array of thePLIIM system, so as to repeatedly illuminate the detector element from adifferent point in space and at a different moment in time over thephoto-integration period of the detector element, thereby destroying thespatial and temporal coherence of the laser illumination beam receivedat the detector element and reducing the speckle-noise level producedthereat;

[0071]FIG. 1G4 is an elevated side view schematic representation of thePLIIM system, taken along line 1G4-1G4 in FIG. 1G1, showing the field ofview of the image formation and detection module being folded in thedownwardly imaging direction by the field of view folding mirror, andthe planar laser illumination beam produced by each planar laserillumination module being directed along the imaging direction such thatboth the folded field of view and stationary planar laser illuminationbeams are arranged in a substantially coplanar relationship duringobject illumination and image detection operations;

[0072]FIG. 1G5 is an elevated side view of the PLIIM system of FIG. 1G1,showing the spatial limits of the fixed field of view (FOV) of the imageformation and detection module when set to image the tallest packagesmoving on a conveyor belt structure, as well as the spatial limits ofthe fixed FOV of the image formation and detection module when set toimage objects having height values close to the surface height of theconveyor belt structure;

[0073]FIG. 1G6 is a perspective view of a first type of light shieldwhich can be used in the PLIIM system of FIG. 1G1, to visually blockportions of planar laser illumination beams that extend beyond thescanning field of the system, but which could pose a health risk tohumans if viewed thereby during system operation;

[0074]FIG. 1G7 is a perspective view of a second type of light shieldwhich can be used in the PLIIM system of FIG. 1G1, to visually blockportions of planar laser illumination beams that extend beyond thescanning field of the system, but which could pose a health risk tohumans if viewed thereby during system operation;

[0075]FIG. 1G8 is a perspective view of one planar laser illuminationarray (PLIA) employed in the PLIIM system of FIG. 1G1, showing an arrayof visible laser diodes (VLDs), each mounted within a VLD mounting blockwherein a focusing lens is mounted and on the end of which there is av-shaped notch or recess, within which a cylindrical lens element ismounted, and wherein each such VLD mounting block is mounted on anL-bracket for mounting within the housing of the PLIIM system;

[0076]FIG. 1G9 is an elevated end view of one planar laser illuminationarray (PLIA) employed in the PLIIM system of FIG. 1G, taken along line1G9-1G9 thereof;

[0077]FIG. 10G10 is an elevated side view of one planar laserillumination array (PLIA) employed in the PLIIM system of FIG. 1G1,taken along line 1G10-G10 thereof, showing a visible laser diode (VLD)and a focusing lens mounted within a VLD mounting block, and acylindrical lens element mounted at the end of the VLD mounting block,so that the central axis of the cylindrical lens element issubstantially perpendicular to the optical axis of the focusing lens;

[0078]FIG. 1G11 is an elevated side view of one of the VLD mountingblocks employed in the PLIIM system of FIG. 1G1, taken along a viewingdirection which is orthogonal to the central axis of the cylindricallens element mounted to the end portion of the VLD mounting block;

[0079]FIG. 1G12 is an elevated plan view of one of VLD mounting blocksemployed in the PLIIM system of FIG. 1G1, taken along a viewingdirection which is parallel to the central axis of the cylindrical lenselement mounted to the VLD mounting block;

[0080]FIG. 1G13 is a perspective view of an optical assembly comprisingthe PLIA of FIG. 1G8 and a PLIB micro-oscillation mechanism realized bya refractive-type cylindrical lens array that is micro-oscillated by apair of ultrasonic transducers arranged in a push-pull configuration soas to micro-oscillate each beam component within the composite planarlaser illumination beam by a relatively small distance with respect toeach detector element in the stationary linear image detection array ofthe PLIIM system, thereby repeatedly illuminating the detector elementfrom a different point in space and at a different moment in time overthe photo-integration period of the detector element, thereby destroyingthe spatial and temporal coherence of the laser illumination beamreceived at the detector element and thus reducing the speckle-noiselevel produced thereat;

[0081]FIG. 1G13A is a geometrical model of a portion of the opticalassembly shown in FIG. 1G13, illustrating the first order parametersinvolved in the process used to mitigate speckle-type noise observed ateach of the elements in the image detection array employed in the PLIIMsystem of the present invention;

[0082]FIG. 1G13B1 is a pictorial representation of a string of numbersimaged by the PLIIM system of the present invention without the use ofthe speckle-noise reduction optics of the present invention;

[0083]FIG. 1G13B2 is a pictorial representation of the same string ofnumbers (shown in FIG. 1G13B1) imaged by the PLIIM system of the presentinvention using the speckle-noise reduction optics of the presentinvention, and showing a significant mitigation in speckle-noise inimages captured by the electronic image detection array of the PLIIMsystem;

[0084]FIG. 1G14 is a perspective view of the refractive-type cylindricallens array employed in the optical assembly shown in FIG. 1G13;

[0085]FIG. 1G15 is a perspective view of the array support frameemployed in the optical assembly shown in FIG. 1G13;

[0086]FIG. 1G16 is a schematic representation of the refractive-typecylindrical lens array employed in FIG. 1G13, shown configured between apair of ultrasonic transducers operated in a push-pull mode ofoperation;

[0087]FIG. 1G17 is a perspective view of an optical assembly comprisingthe PLIA of FIG. 1G8 and a PLIB micro-oscillation mechanism realized by(a holographically-fabricated) diffractive-type cylindrical lens arraythat is micro-oscillated by a pair of ultrasonic transducers arranged ina push-pull configuration so as to micro-oscillate each beam componentwithin the composite planar laser illumination beam by a relativelysmall distance with respect to each detector element in the stationarylinear image detection array of the PLIIM system, thereby repeatedlyilluminating the detector element from a different point in space and ata different moment in time over the photo-integration period of thedetector element, thereby destroying the spatial and temporal coherenceof the laser illumination beam received at the detector element and thusreducing the speckle-noise level produced thereat;

[0088]FIG. 1G18 is a perspective view of the refractive-type cylindricallens array employed in the optical assembly shown in FIG. 1G17;

[0089]FIG. 1G19 is a perspective view of the array support frameemployed in the optical assembly shown in FIG. 1G17;

[0090]FIG. 1G20 is a schematic representation of the refractive-typecylindrical lens array employed in FIG. 1G17, shown configured between apair of ultrasonic transducers operated in a push-pull mode ofoperation;

[0091]FIG. 1G21 is a perspective view of an optical assembly comprisingthe PLIA of FIG. 1G8 and a PLIB micro-oscillation mechanism realized bya stationary reflective element fixedly mounted in front of arefractive-type cylindrical lens array, and a pair of micro-oscillatingreflective elements that are micro-oscillated about a common pivot pointby a pair of ultrasonic transducers arranged in a push-pullconfiguration so as to micro-oscillate each beam component within thecomposite planar laser illumination beam by a relatively small distancewith respect to each detector element in the stationary linear imagedetection array of the PLIIM system, thereby repeatedly illuminating thedetector element from a different point in space and at a differentmoment in time over the photo-integration period of the detectorelement, thereby destroying the spatial and temporal coherence of thelaser illumination beam received at the detector element and thusreducing the speckle-noise level produced thereat;

[0092]FIG. 1G23 is a schematic representation, taken along an elevatedside view of the optical assembly shown in FIG. 1G21, showing theoptical path which the laser illumination beam produced thereby travelstowards the target object to be illuminated;

[0093]FIG. 1G24 is a schematic representation of one micro-oscillatingreflective element in the pair employed in FIG. 1G21, shown configuredbetween a pair of ultrasonic transducers operated in a push-pull mode ofoperation, so as to undergo micro-oscillation;

[0094]FIG. 1G25 is a perspective view of an optical assembly comprisingthe PLIA of FIG. 1G8 and a PLIB micro-oscillation mechanism realized byan electro-acoustic (i.e. Bragg Cell) beam deflection device throughwhich each laser beam within the PLIM is transmitted and deflected inresponse to acoustical signals propagating through theelectro-acoustical device so as to micro-oscillate each beam componentwithin the composite planar laser illumination beam by a relativelysmall distance with respect to each detector element in the stationarylinear image detection array of the PLIIM system, thereby repeatedlyilluminating the detector element from a different point in space and ata different moment in time over the photo-integration period of thedetector element, thereby destroying the spatial and temporal coherenceof the laser illumination beam received at the detector element and thusreducing the speckle-noise level produced thereat;

[0095]FIG. 1G26 is a schematic representation, taken along thecross-section of the optical assembly shown in FIG. 1G25, showing theoptical path of each laser beam within the PLIM travels on its waytowards the target object to be illuminated;

[0096]FIG. 1H1 is an elevated side view of the collimating lens elementinstalled within each VLD mounting block employed in the PLIIM system ofFIG. 1G1;

[0097]FIG. 1H2 is an axial view of the collimating lens elementinstalled within each VLD mounting block employed in the PLIIM system ofFIG. 1G1;

[0098]FIG. 1I1 is an elevated plan view of one of planar laserillumination modules (PLIMs) employed in the PLIIM system of FIG. 1G1,taken along a viewing direction which is parallel to the central axis ofthe cylindrical lens element mounted in the VLD mounting block thereof,showing that the cylindrical lens element expands (i.e. spreads out) thelaser beam along the direction of beam propagation so that asubstantially planar laser illumination beam is produced, which ischaracterized by a plane of propagation that is coplanar with thedirection of beam propagation;

[0099]FIG. 1I2 is an elevated plan view of one of the PLIMs employed inthe PLIIM system of FIG. 1G1, taken along a viewing direction which isperpendicular to the central axis of the cylindrical lens elementmounted within the axial bore of the VLD mounting block thereof, showingthat the focusing lens planar focuses the laser beam to its minimum beamwidth at a point which is the farthest distance at which the system isdesigned to capture images, while the cylindrical lens element does notexpand or spread out the laser beam in the direction normal to the planeof propagation of the planar laser illumination beam;

[0100]FIG. 1J1 is a geometrical optics model for the imaging subsystememployed in the linear-type image formation and detection module in thePLIIM system of the first generalized embodiment shown in FIG. 1A;

[0101]FIG. 1J2 is a geometrical optics model for the imaging subsystemand linear image detection array employed in linear-type image detectionarray employed in the image formation and detection module in the PLIIMsystem of the first generalized embodiment shown in FIG. 1A;

[0102]FIG. 1J3 is a graph, based on thin lens analysis, showing that theimage distance at which light is focused through a thin lens is afunction of the object distance at which the light originates;

[0103]FIG. 1J4 is a schematic representation of an imaging subsystemhaving a variable focal distance lens assembly, wherein a group of lenscan be controllably moved along the optical axis of the subsystem, andhaving the effect of changing the image distance to compensate for achange in object distance, allowing the image detector to remain inplace;

[0104]FIG. 1J5 is schematic representation of a variable focal length(zoom) imaging subsystem which is capable of changing its focal lengthover a given range; so that a longer focal length produces a smallerfield of view at a given object distance;

[0105]FIG. 1J6 is a schematic representation of an illustrativeembodiment of the image formation and detection (IFD) module employed inthe PLIIM systems of the present invention, wherein various opticalparameters used to model the system are defined and graphicallyindicated wherever possible;

[0106]FIG. 1K1 is a schematic representation illustrating how the fieldof view of a PLIIM system can be fixed to substantially match the scanfield width thereof (measured at the top of the scan field) at asubstantial distance above a conveyor belt;

[0107]FIG. 1K2 is a schematic representation illustrating how the fieldof view of a PLIIM system can be fixed to substantially match the scanfield width of a low profile scanning field slightly above the conveyorbelt surface, by fixed the focal length of the imaging subsystem duringthe optical design stage;

[0108]FIG. 1L is a schematic representation illustrating how anarrangement of FOV beam folding mirrors can be used to produce anexpanded FOV that matches the geometrical characteristics of thescanning application at hand, when the FOV emerges from the systemhousing;

[0109]FIG. 1L2 is a schematic representation illustrating how the fixedfield of view of an imaging subsystem can be expanded across a workingspace (e.g. conveyor belt structure) by rotating the FOV during objectillumination and imaging operations;

[0110]FIG. 1M1 shows a data plot of pixel power density E_(pix) vs.object distance r calculated using the arbitrary but reasonable valuesE_(o)=1 W/m², f=80 mm and F=4.5, demonstrating that, in acounter-intuitive manner, the power density at the pixel (and thereforethe power incident on the pixel, since its area remains constant)actually increases as the object distance increases;

[0111]FIG. 1M2 is data plot of laser beam power density vs. positionalong the planar laser beam width showing that the total output power inthe planar laser illumination beam of the present invention isdistributed along the width of the beam in a roughly Gaussiandistribution;

[0112]FIG. 1M3 shows a plot of beam width length L vs. object distance rcalculated using a beam fan/spread angle θ=50°, demonstrating that theplanar laser beam width increases as a function of increasing objectdistance;

[0113]FIG. 1M4 is a typical data plot of planar laser beam height h vs.image distance r for a planar laser illumination beam of the presentinvention focused at the farthest working distance in accordance withthe principles of the present invention, demonstrating that the heightdimension of the planar laser beam decreases as a function of increasingobject distance;

[0114]FIG. 1N is a data plot of planar laser beam power density E o atthe center of its beam width, plotted as a function of object distance,demonstrating that use of the laser beam focusing technique of thepresent invention, wherein the height of the planar laser illuminationbeam is decreased as the object distance increases, compensates for theincrease in beam width in the planar laser illumination beam, whichoccurs for an increase in object distance, thereby yielding a laser beampower density on the target object which increases as a function ofincreasing object distance over a substantial portion of the objectdistance range of the PLIIM system;

[0115]FIG. 1O is a data plot of pixel power density E₀ vs. objectdistance, obtained when using a planar laser illumination beam whosebeam height decreases with increasing object distance, and also a dataplot of the “reference” pixel power density plot E_(pix) vs. objectdistance obtained when using a planar laser illumination beam whose beamheight is substantially constant (e.g. 1 mm) over the entire portion ofthe object distance range of the PLIIM system;

[0116]FIG. 1P1 is a schematic representation of the composite powerdensity characteristics associated with the planar laser illuminationarray in the PLIIM system of FIG. 1G1, taken at the “near field region”of the system, and resulting from the additive contributions of theindividual visible laser diodes in the planar laser illumination arrays;

[0117]FIG. 1P2 is a schematic representation of the composite powerdensity characteristics associated with the planar laser illuminationarray in the PLIIM system of FIG. 1G1, taken at the “far field region”of the system, and resulting from the additive contributions of theindividual visible laser diodes in the planar laser illumination arrays;

[0118]FIG. 1Q1 is a schematic representation of second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.1A, shown comprising a linear image formation and detection module, anda pair of planar laser illumination arrays arranged in relation to theimage formation and detection module such that the field of view thereofis oriented in a direction that is coplanar with the plane of thestationary planar laser illumination beams produced by the planar laserillumination arrays, without using any laser beam or field of viewfolding mirrors;

[0119]FIG. 1Q2 is a block schematic diagram of the PLIIM system shown inFIG. 1Q1, comprising a linear image formation and detection module, apair of planar laser illumination arrays, an image frame grabber, animage data buffer, a decode image processor, and a system controller;

[0120]FIG. 1R1 is a schematic representation of third illustrativeembodiment of the PLIIM system of the present invention shown in FIG.1A, shown comprising a linear image formation and detection modulehaving a field of view, a pair of planar laser illumination arrays forproducing first and second stationary planar laser illumination beams,and a pair of stationary planar laser beam folding mirrors arranged soas to fold the optical paths of the first and second planar laserillumination beams such that the planes of the first and secondstationary planar laser illumination beams are in a direction that iscoplanar with the field of view of the image formation and detectionmodule;

[0121]FIG. 1R2 is a block schematic diagram of the PLIIM system shown inFIG. 1P1, comprising a linear image formation and detection module, astationary field of view folding mirror, a pair of planar illuminationarrays, a pair of stationary planar laser illumination beam foldingmirrors, an image frame grabber, an image data buffer, a decode imageprocessor, and a system controller;

[0122]FIG. 1S1 is a schematic representation of fourth illustrativeembodiment of the PLIIM system of the present invention shown in FIG.1A, shown comprising a linear image formation and detection modulehaving a field of view (FOV), a stationary field of view (FOV) foldingmirror for folding the field of view of the image formation anddetection module, a pair of planar laser illumination arrays forproducing first and second stationary planar laser illumination beams,and a pair of stationary planar laser illumination beam folding mirrorsfor folding the optical paths of the first and second stationary planarlaser illumination beams so that planes of first and second stationaryplanar laser illumination beams are in a direction that is coplanar withthe field of view of the image formation and detection module;

[0123]FIG. 1S2 is a block schematic diagram of the PLIIM system shown inFIG. 1S1, comprising a linear-type image formation and detection module,a stationary field of view folding mirror, a pair of planar laserillumination arrays, a pair of stationary planar laser beam foldingmirrors, an image frame grabber, an image data buffer, a decode imageprocessor, and a system controller;

[0124]FIG. 1T is a schematic representation of an under (or over) theconveyor belt package identification system embodying the PLIIM systemof FIG. 1A;

[0125]FIG. 1U is a schematic representation of a hand-supportable barcode symbol reading system embodying the PLIIM system of FIG. 1A;

[0126]FIG. 1V1 is a is a schematic representation of second generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of a linear type image formation and detection module (IFDM)having a field of view, such that the planar laser illumination arraysproduce a plane of laser beam illumination (i.e. light) which isdisposed substantially coplanar with the field of view of the imageformation and detection module, and that the planar laser illuminationbeam and the field of view of the image formation and detection modulemove synchronously while maintaining their coplanar relationship witheach other as the planar laser illumination beam is automaticallyscanned over a 2-D region of space during object illumination and imagedetection operations;

[0127]FIG. 1V2 is a schematic representation of first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.1V1, shown comprising an image formation and detection module having afield of view (FOV), a field of view (FOV) folding/sweeping mirror forfolding the field of view of the image formation and detection module, apair of planar laser illumination arrays for producing first and secondplanar laser illumination beams, and a pair of planar laser beamfolding/sweeping mirrors, jointly or synchronously movable with the FOVfolding/sweeping mirror, and arranged so as to fold and sweep theoptical paths of the first and second planar laser illumination beams,so that the folded field of view of the image formation and detectionmodule is synchronously moved with the planar laser illumination beamsin a direction that is coplanar therewith as the planar laserillumination beams are scanned over a 2-D region of space under thecontrol of the system controller;

[0128]FIG. 1V3 is a block schematic diagram of the PLIIM system shown inFIG. 1V1, comprising a pair of planar illumination arrays, a pair ofplanar laser beam folding/sweeping mirrors, a linear-type imageformation and detection module, a field of view folding/sweeping mirror,an image frame grabber, an image data buffer, a decode image processor,and a system controller;

[0129]FIG. 1V4 is a schematic representation of an over-the-conveyorbelt package identification system embodying the PLIIM system of FIG.1V1;

[0130]FIG. 1V5 is a schematic representation of a presentation-type barcode symbol reading system embodying the PLIIM system of FIG. 1V1;

[0131]FIG. 2A is a schematic representation of a third generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of a linear (i.e. 1-dimensional) type image formation anddetection module (IFDM) having a fixed focal length imaging lens, avariable focal distance and a fixed field of view (FOV), so that theplanar laser illumination arrays produce a plane of laser beamillumination which is disposed substantially coplanar with the fieldview of the image formation and detection module during objectillumination and image detection operations carried out on bar codesymbol structures and other graphical indicia which may embodyinformation within its structure;

[0132]FIG. 2B1 is a schematic representation of a first illustrativeembodiment of the PLIIM system shown in FIG. 2A, comprising an imageformation and detection module having a field of view (FOV), and a pairof planar laser illumination arrays for producing first and secondstationary planar laser illumination beams in an imaging direction thatis coplanar with the field of view of the image formation and detectionmodule;

[0133]FIG. 2B2 is a schematic representation of the PLIIM system of thepresent invention shown in FIG. 2B1, wherein the linear image formationand detection module is shown comprising a linear array ofphoto-electronic detectors realized using CCD technology, and eachplanar laser illumination array is shown comprising an array of planarlaser illumination modules;

[0134]FIG. 2C1 is a block schematic diagram of the PLIIM system shown inFIG. 2B1, comprising a pair of planar illumination arrays, a linear-typeimage formation and detection module, an image frame grabber, an imagedata buffer, a decode image processor, and a system controller;

[0135]FIG. 2C2 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 2B1, wherein an imaging subsystem having a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

[0136]FIG. 2D1 is a schematic representation of the second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.2A, shown comprising a linear image formation and detection module, astationary field of view (FOV) folding mirror for folding the field ofview of the image formation and detection module, and a pair of planarlaser illumination arrays arranged in relation to the image formationand detection module such that the folded field of view is oriented inan imaging direction that is coplanar with the stationary planes oflaser illumination produced by the planar laser illumination arrays;

[0137]FIG. 2D2 is a block schematic diagram of the PLIIM system shown inFIG. 2D1, comprising a pair of planar laser illumination arrays (PLIAs),a linear-type image formation and detection module, a stationary fieldof view of folding mirror, an image frame grabber, an image data buffer,a decode image processor, and a system controller;

[0138]FIG. 2D3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 2D1, wherein an imaging subsystem having a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

[0139]FIG. 2E1 is a schematic representation of the third illustrativeembodiment of the PLIIM system of the present invention shown in FIG.1A, shown comprising an image formation and detection module having afield of view (FOV), a pair of planar laser illumination arrays forproducing first and second stationary planar laser illumination beams, apair of stationary planar laser beam folding mirrors for folding thestationary (i.e. non-swept) planes of the planar laser illuminationbeams produced by the pair of planar laser illumination arrays, in animaging direction that is coplanar with the stationary plane of thefield of view of the image formation and detection module during systemoperation;

[0140]FIG. 2E2 is a block schematic diagram of the PLIIM system shown inFIG. 2B1, comprising a pair of planar laser illumination arrays, alinear image formation and detection module, a pair of stationary planarlaser illumination beam folding mirrors, an image frame grabber, animage data buffer, a decode image processor, and a system controller;

[0141]FIG. 2E3 is a schematic representation of the linear imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 2B1, wherein an imaging subsystem having fixed focal lengthimaging lens, a variable focal distance and a fixed field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

[0142]FIG. 2F1 is a schematic representation of the fourth illustrativeembodiment of the PLIIM system of the present invention shown in FIG.2A, shown comprising a linear image formation and detection modulehaving a field of view (FOV), a stationary field of view (FOV) foldingmirror, a pair of planar laser illumination arrays for producing firstand second stationary planar laser illumination beams, and a pair ofstationary planar laser beam folding mirrors arranged so as to fold theoptical paths of the first and second stationary planar laserillumination beams so that these planar laser illumination beams areoriented in an imaging direction that is coplanar with the folded fieldof view of the linear image formation and detection module;

[0143]FIG. 2F2 is a block schematic diagram of the PLIIM system shown inFIG. 2F1, comprising a pair of planar illumination arrays, a linearimage formation and detection module, a stationary field of view (FOV)folding mirror, a pair of stationary planar laser illumination beamfolding mirrors, an image frame grabber, an image data buffer, a decodeimage processor, and a system controller;

[0144]FIG. 2F3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 2F1, wherein an imaging subsystem having a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

[0145]FIG. 2G is a schematic representation of an over-the-conveyor beltpackage identification system embodying the PLIIM system of FIG. 2A;

[0146]FIG. 2H is a schematic representation of a hand-supportable barcode symbol reading system embodying the PLIIM system of FIG. 2A;

[0147]FIG. 2I1 is a schematic representation of the fourth generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of a linear image formation and detection module (IFDM) having afixed focal length imaging lens, a variable focal distance and fixedfield of view (FOV), so that the planar illumination arrays produces aplane of laser beam illumination which is disposed substantiallycoplanar with the field view of the image formation and detection moduleand synchronously moved therewith while the planar laser illuminationbeams are automatically scanned over a 2-D region of space during objectillumination and imaging operations;

[0148]FIG. 2I2 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.2I1, shown comprising an image formation and detection module having afield of view (FOV), a field of view (FOV) folding/sweeping mirror, apair of planar laser illumination arrays for producing first and secondplanar laser illumination beams, and a pair of planar laser beamfolding/sweeping mirrors, jointly movable with the FOV folding/sweepingmirror, and arranged so that the field of view of the image formationand detection module is coplanar with the folded planes of first andsecond planar laser illumination beams, and the coplanar FOV and planarlaser illumination beams are synchronously moved together while theplanar laser illumination beams and FOV are scanned over a 2-D region ofspace containing a stationary or moving bar code symbol or othergraphical structure (e.g. text) embodying information;

[0149]FIG. 2I3 is a block schematic diagram of the PLIIM system shown inFIGS. 2I1 and 2I2, comprising a pair of planar illumination arrays, alinear image formation and detection module, a field of view (FOV)folding/sweeping mirror, a pair of planar laser illumination beamfolding/sweeping mirrors jointly movable therewith, an image framegrabber, an image data buffer, a decode image processor, and a systemcontroller;

[0150]FIG. 2I4 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIGS. 2I1 and 2I2, wherein an imaging subsystem having a fixed focallength imaging lens, a variable focal distance and a fixed field of viewis arranged on an optical bench, mounted within a compact modulehousing, and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

[0151]FIG. 2I5 is a schematic representation of a hand-supportable barcode symbol reader embodying the PLIIM system of FIG. 2I1;

[0152]FIG. 2I6 is a schematic representation of a presentation-type barcode symbol reader embodying the PLIIM system of FIG. 2I1;

[0153]FIG. 3A is a schematic representation of a fifth generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of a linear image formation and detection module (IFDM) having avariable focal length imaging lens, a variable focal distance and avariable field of view, so that the planar laser illumination arraysproduce a stationary plane of laser beam illumination (i.e. light) whichis disposed substantially coplanar with the field view of the imageformation and detection module during object illumination and imagedetection operations carried out on bar code symbol and other graphicalindicia by the PLIIM system of the present invention;

[0154]FIG. 3B1 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3A, shown comprising an image formation and detection module, and a pairof planar laser illumination arrays arranged in relation to the imageformation and detection module such that the stationary field of viewthereof is oriented in an imaging direction that is coplanar with thestationary plane of laser illumination produced by the planar laserillumination arrays, without using any laser beam or field of viewfolding mirrors.

[0155]FIG. 3B2 is a schematic representation of the first illustrativeembodiment of the PLIIM system shown in FIG. 3B1, wherein the linearimage formation and detection module is shown comprising a linear arrayof photo-electronic detectors realized using CCD technology, and eachplanar laser illumination array is shown comprising an array of planarlaser illumination modules;

[0156]FIG. 3C1 is a block schematic diagram of the PLIIM shown in FIG.3B1, comprising a pair of planar laser illumination arrays, a linearimage formation and detection module, an image frame grabber, an imagedata buffer, a decode image processor, and a system controller;

[0157]FIG. 3C2 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 3B1, wherein an imaging subsystem having a variable focal lengthimaging lens, a variable focal distance and a variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system;

[0158]FIG. 3D is a schematic representation of an illustrativeimplementation of the imaging subsystem contained in the image formationand detection module employed in the PLIIM system of FIG. 3B1, showncomprising a stationary lens system mounted before the stationary linearimage detection array, a first movable lens system for large steppedmovement relative to the stationary lens system during image zoomingoperations, and a second movable lens system for small stepped movementsrelative to the first movable lens system and the stationary lens systemduring image focusing operations;

[0159]FIG. 3E1 is a schematic representation of the second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3A, shown comprising a linear image formation and detection module, apair of planar laser illumination arrays, and a stationary field of view(FOV) folding mirror arranged in relation to the image formation anddetection module such that the stationary field of view thereof isoriented in an imaging direction that is coplanar with the stationaryplane of laser illumination produced by the planar laser illuminationarrays, without using any planar laser illumination beam foldingmirrors;

[0160]FIG. 3E2 is a block schematic diagram of the PLIIM system shown inFIG. 3E1, comprising a pair of planar illumination arrays, a linearimage formation and detection module, a stationary field of view (FOV)folding mirror, an image frame grabber, an image data buffer, a decodeimage processor, and a system controller;

[0161]FIG. 3E3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 3E1, wherein an imaging subsystem having a variable focal lengthimaging lens, a variable focal distance and a variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system;

[0162]FIG. 3E4 is a schematic representation of the PLIIM system of FIG.3E1, shown comprising a linear-type image formation and detectionmodule, a pair of planar laser illumination arrays, and a field of view(FOV) folding mirror for folding the field of view of the imageformation and detection module in a direction that is coplanar with theplane of laser illumination produced by the planar illumination arrays;

[0163]FIG. 3E5 is a plan view schematic representation of the PLIIMsystem, taken along line 3E5-3E5 in FIG. 3E4, showing the spatial extentof the field of view of the image formation and detection module in theillustrative embodiment of the present invention;

[0164]FIG. 3E6 is an elevated end view schematic representation of thePLIIM system, taken along line 3E6-3E6 in FIG. 3E4, showing the field ofview of the linear image formation and detection module being folded inthe downwardly imaging direction by the field of view folding mirror,and the planar laser illumination beam produced by each planar laserillumination module being directed in the imaging direction such thatboth the folded field of view and planar laser illumination beams arearranged in a substantially coplanar relationship during objectillumination and imaging operations;

[0165]FIG. 3E7 is an elevated side view schematic representation of thePLIIM system, taken along line 3E7-3E7 in FIG. 3E4, showing the field ofview of the linear image formation and detection module being folded inthe downwardly imaging direction by the field of view folding mirror,and the planar laser illumination beam produced by each planar laserillumination module being directed along the imaging direction such thatboth the folded field of view and stationary planar laser illuminationbeams are arranged in a substantially coplanar relationship duringobject illumination and image detection operations;

[0166]FIG. 3E8 is an elevated side view of the PLIIM system of FIG. 3E4,showing the spatial limits of the variable field of view (FOV) of thelinear image formation and detection module when controllably adjustedto image the tallest packages moving on a conveyor belt structure, aswell as the spatial limits of the variable FOV of the linear imageformation and detection module when controllably adjusted to imageobjects having height values close to the surface height of the conveyorbelt structure;

[0167]FIG. 3F1 is a schematic representation of the third illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3A, shown comprising a linear image formation and detection modulehaving a field of view (FOV), a pair of planar laser illumination arraysfor producing first and second stationary planar laser illuminationbeams, a pair of stationary planar laser illumination beam foldingmirrors arranged relative to the planar laser illumination arrays so asto fold the stationary planar laser illumination beams produced by thepair of planar illumination arrays in an imaging direction that iscoplanar with stationary field of view of the image formation anddetection module during illumination and imaging operations;

[0168]FIG. 3F2 is a block schematic diagram of the PLIIM system shown inFIG. 3FF1, comprising a pair of planar illumination arrays, a linearimage formation and detection module, a pair of stationary planar laserillumination beam folding mirrors, an image frame grabber, an image databuffer, a decode image processor, and a system controller;

[0169]FIG. 3F3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 3F1, wherein an imaging subsystem having a variable focal lengthimaging lens, a variable focal distance and a variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system during illumination and imagingoperations;

[0170]FIG. 3G1 is a schematic representation of the fourth illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3A, shown comprising a linear image formation and detection modulehaving a field of view (FOV), a pair of planar laser illumination arraysfor producing first and second stationary planar laser illuminationbeams, a stationary field of view (FOV) folding mirror for folding thefield of view of the image formation and detection module, and a pair ofstationary planar laser beam folding mirrors arranged so as to fold theoptical paths of the first and second planar laser illumination beamssuch that stationary planes of first and second planar laserillumination beams are in an imaging direction which is coplanar withthe field of view of the image formation and detection module duringillumination and imaging operations;

[0171]FIG. 3G2 is a block schematic diagram of the PLIIM system shown inFIG. 3G1, comprising a pair of planar illumination arrays, a linearimage formation and detection module, a stationary field of view (FOV)folding mirror, a pair of stationary planar laser illumination beamfolding mirrors, an image frame grabber, an image data buffer, a decodeimage processor, and a system controller;

[0172]FIG. 3G3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 3G1, wherein an imaging subsystem having a variable focal lengthimaging lens, a variable focal distance and a variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system during illumination and imagingoperations;

[0173]FIG. 3H is a schematic representation of an over-the-conveyor andside of conveyor belt package identification systems embodying the PLIIMsystem of FIG. 3A;

[0174]FIG. 3I is a schematic representation of a hand-supportable barcode symbol reading device embodying the PLIIM system of FIG. 3A;

[0175]FIG. 3J1 is a schematic representation of the sixth generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of a linear image formation and detection module (IFDM) having avariable focal length imaging lens, a variable focal distance and avariable field of view, so that the planar illumination arrays produce aplane of laser beam illumination which is disposed substantiallycoplanar with the field view of the image formation and detection moduleand synchronously moved therewith as the planar laser illumination beamsare scanned across a 2-D region of space during object illumination andimage detection operations;

[0176]FIG. 3J2 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3J1, shown comprising an image formation and detection module having afield of view (FOV), a pair of planar laser illumination arrays forproducing first and second planar laser illumination beams, a field ofview folding/sweeping mirror for folding and sweeping the field of viewof the image formation and detection module, and a pair of planar laserbeam folding/sweeping mirrors jointly movable with the FOVfolding/sweeping mirror and arranged so as to fold the optical paths ofthe first and second planar laser illumination beams so that the fieldof view of the image formation and detection module is in an imagingdirection that is coplanar with the planes of first and second planarlaser illumination beams during illumination and imaging operations;

[0177]FIG. 3J3 is a block schematic diagram of the PLIIM system shown inFIG. 3J1 and 3J2, comprising a pair of planar illumination arrays, alinear image formation and detection module, a field of viewfolding/sweeping mirror, a pair of planar laser illumination beamfolding/sweeping mirrors, an image frame grabber, an image data buffer,a decode image processor, and a system controller;

[0178]FIG. 3J4 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIGS. 3J1 and J2, wherein an imaging subsystem having a variablefocal length imaging lens, a variable focal distance and a variablefield of view is arranged on an optical bench, mounted within a compactmodule housing, and responsive to zoom and focus control signalsgenerated by the system controller of the PLIIM system duringillumination and imaging operations;

[0179]FIG. 3J5 is a schematic representation of a hand-held bar codesymbol reading system embodying the PLIIM subsystem of FIG. 3J1;

[0180]FIG. 3J6 is a schematic representation of a presentation-type barcode symbol reading system embodying the PLIIM subsystem of FIG. 3J1;

[0181]FIG. 4A is a schematic representation of a seventh generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of an area (i.e. 2-dimensional) type image formation and detectionmodule (IFDM) having a fixed focal length camera lens, a fixed focaldistance and fixed field of view projected through a 3-D scanningregion, so that the planar illumination arrays produce a plane of laserbeam illumination which is disposed substantially coplanar with sectionsof the field view of the image formation and detection module while theplanar laser illumination beam is automatically scanned across the 3-Dscanning region during object illumination and imaging operationscarried out on a bar code symbol or other graphical indicia by the PLIIMsystem;

[0182]FIG. 4B1 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.4A, shown comprising an area image formation and detection module havinga field of view (FOV) projected through a 3-D scanning region, a pair ofplanar laser illumination arrays for producing first and second planarlaser illumination beams, and a pair of planar laser beamfolding/sweeping mirrors for folding and sweeping the planar laserillumination beams so that the optical paths of these planar laserillumination beams are oriented in an imaging direction that is coplanarwith a section of the field of view of the image formation and detectionmodule as the planar laser illumination beams are swept through the 3-Dscanning region during object illumination and imaging operations;

[0183]FIG. 4B2 is a schematic representation of PLIIM system shown inFIG. 4B1, wherein the linear image formation and detection module isshown comprising an area (2-D) array of photo-electronic detectorsrealized using CCD technology, and each planar laser illumination arrayis shown comprising an array of planar laser illumination modules;

[0184]FIG. 4B3 is a block schematic diagram of the PLIIM system shown inFIG. 4B1, comprising a pair of planar illumination arrays, an area-typeimage formation and detection module, a pair of planar laserillumination beam sweeping mirrors, an image frame grabber, an imagedata buffer, a decode image processor, and a system controller;

[0185]FIG. 4C1 is a schematic representation of the second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.4A, comprising a area image formation and detection module having afield of view (FOV), a pair of planar laser illumination arrays forproducing first and second planar laser illumination beams, a stationaryfield of view folding mirror for folding and projecting the field ofview through a 3-D scanning region, and a pair of planar laser beamfolding/sweeping mirrors for folding and sweeping the planar laserillumination beams so that the optical paths of these planar laserillumination beams are oriented in an imaging direction that is coplanarwith a section of the field of view of the image formation and detectionmodule as the planar laser illumination beams are swept through the 3-Dscanning region during object illumination and imaging operations;

[0186]FIG. 4C2 is a block schematic diagram of the PLIIM system shown inFIG. 4C1, comprising a pair of planar illumination arrays, an area-typeimage formation and detection module, a movable field of view foldingmirror, a pair of planar laser illumination beam sweeping mirrorsjointly or otherwise synchronously movable therewith, an image framegrabber, an image data buffer, a decode image processor, and a systemcontroller;

[0187]FIG. 4D is a schematic representation of presentation-typeholder-under bar code symbol reading system embodying the PLIIMsubsystem of FIG. 4A;

[0188]FIG. 4E is a schematic representation of hand-supportable-type barcode symbol reading system embodying the PLIIM subsystem of FIG. 4A;

[0189]FIG. 5A is a schematic representation of an eighth generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of an area (i.e. 2-dimensional) type image formation and detectionmodule (IFDM) having a fixed focal length imaging lens, a variable focaldistance and a fixed field of view (FOV) projected through a 3-Dscanning region, so that the planar laser illumination arrays produce aplane of laser beam illumination which is disposed substantiallycoplanar with sections of the field view of the image formation anddetection module as the planar laser illumination beams areautomatically scanned through the 3-D scanning region during objectillumination and image detection operations carried out on a bar codesymbol or other graphical indicia by the PLIIM system;

[0190]FIG. 5B1 is a schematic representation of the first illustrativeembodiment of the PLIIM system shown in FIG. 5A, shown comprising animage formation and detection module having a field of view (FOV)projected through a 3-D scanning region, a pair of planar laserillumination arrays for producing first and second planar laserillumination beams, and a pair of planar laser beam folding/sweepingmirrors for folding and sweeping the planar laser illumination beams sothat the optical paths of these planar laser illumination beams areoriented in an imaging direction that is coplanar with a section of thefield of view of the image formation and detection module as the planarlaser illumination beams are swept through the 3-D scanning regionduring object illumination and imaging operations;

[0191]FIG. 5B2 is a schematic representation of the first illustrativeembodiment of the PLIIM system shown in FIG. 5B1, wherein the linearimage formation and detection module is shown comprising an area (2-D)array of photo-electronic detectors realized using CCD technology, andeach planar laser illumination array is shown comprising an array ofplanar laser illumination modules;

[0192]FIG. 5B3 is a block schematic diagram of the PLIIM system shown inFIG. 5B1, comprising a short focal length imaging lens, a low-resolutionimage detection array and associated image frame grabber, a pair ofplanar illumination arrays, a high-resolution area-type image formationand detection module, a pair of planar laser beam folding/sweepingmirrors, an associated image frame grabber, an image data buffer, adecode image processor, and a system controller;

[0193]FIG. 5B4 is a schematic representation of the area-type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 5B1, wherein an imaging subsystem having a fixed length imaginglens, a variable focal distance and fixed field of view is arranged onan optical bench, mounted within a compact module housing, andresponsive to focus control signals generated by the system controllerof the PLIIM system during illumination and imaging operations;

[0194]FIG. 5C1 is a schematic representation of the second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.5A, shown comprising an image formation and detection module, astationary FOV folding mirror for folding and projecting the FOV througha 3-D scanning region, a pair of planar laser illumination arrays, andpair of planar laser beam folding/sweeping mirrors for folding andsweeping the planar laser illumination beams so that the optical pathsof these planar laser illumination beams are oriented in an imagingdirection that is coplanar with a section of the field of view of theimage formation and detection module as the planar laser illuminationbeams are swept through the 3-D scanning region during objectillumination and imaging operations;

[0195]FIG. 5C2 is a schematic representation of the second illustrativeembodiment of the PLIIM system shown in FIG. 6A, wherein the linearimage formation and detection module is shown comprising an area (2-D)array of photo-electronic detectors realized using CCD technology, andeach planar laser illumination array is shown comprising an array ofplanar laser illumination modules;

[0196]FIG. 5C3 is a block schematic diagram of the PLIIM system shown inFIG. 5C1, comprising a pair of planar illumination arrays, an area-typeimage formation and detection module, a stationary field of view (FOV)folding mirror, a pair of planar laser illumination beam folding andsweeping mirrors, an image frame grabber, an image data buffer, a decodeimage processor, and a system controller;

[0197]FIG. 5C4 is a schematic representation of the area-type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 5C1, wherein an imaging subsystem having a fixed length imaginglens, a variable focal distance and fixed field of view is arranged onan optical bench, mounted within a compact module housing, andresponsive to focus control signals generated by the system controllerof the PLIIM system during illumination and imaging operations;

[0198]FIG. 5D is a schematic representation of a presentation-typehold-under bar code symbol reading system embodying the PLIIM subsystemof FIG. 5A;

[0199]FIG. 6A is a schematic representation of a ninth generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of an area type image formation and detection module (IFDM) havinga variable focal length imaging lens, a variable focal distance andvariable field of view projected through a 3-D scanning region, so thatthe planar laser illumination arrays produce a plane of laser beamillumination which is disposed substantially coplanar with sections ofthe field view of the image formation and detection module as the planarlaser illumination beams are automatically scanned through the 3-Dscanning region during object illumination and image detectionoperations carried out on a bar code symbol or other graphical indiciaby the PLIIM system;

[0200]FIG. 6B1 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.6A, shown comprising an image formation and detection module, a pair ofplanar laser illumination arrays for producing first and second planarlaser illumination beams, a pair of planar laser illumination arrays forproducing first and second planar laser illumination beams, and a pairof planar laser beam folding/sweeping mirrors for folding and sweepingthe planar laser illumination beams so that the optical paths of theseplanar laser illumination beams are oriented in an imaging directionthat is coplanar with a section of the field of view of the imageformation and detection module as the planar laser illumination beamsare swept through the 3-D scanning region during object illumination andimaging operations;

[0201]FIG. 6B2 is a schematic representation of a first illustrativeembodiment of the PLIIM system shown in FIG. 6B1, wherein the area imageformation and detection module is shown comprising an area array ofphoto-electronic detectors realized using CCD technology, and eachplanar laser illumination array is shown comprising an array of planarlaser illumination modules;

[0202]FIG. 6B3 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.6B1, shown comprising a pair of planar illumination arrays, an area-typeimage formation and detection module, a pair of planar laser beamfolding/sweeping mirrors, an image frame grabber, an image data buffer,a decode image processor, and a system controller;

[0203]FIG. 6B4 is a schematic representation of the area-type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 6B1, wherein an imaging subsystem having a variable lengthimaging lens, a variable focal distance and variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system during illumination and imagingoperations;

[0204]FIG. 6C1 is a schematic representation of the second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.6A, shown comprising an image formation and detection module, astationary FOV folding mirror for folding and projecting the FOV througha 3-D scanning region, a pair of planar laser illumination arrays, andpair of planar laser beam folding/sweeping mirrors for folding andsweeping the planar laser illumination beams so that the optical pathsof these planar laser illumination beams are oriented in an imagingdirection that is coplanar with a section of the field of view of theimage formation and detection module as the planar laser illuminationbeams are swept through the 3-D scanning region during objectillumination and imaging operations;

[0205]FIG. 6C2 is a schematic representation of a second illustrativeembodiment of the PLIIM system shown in FIG. 6C1, wherein the area imageformation and detection module is shown comprising an area array ofphoto-electronic detectors realized using CCD technology, and eachplanar laser illumination array is shown comprising an array of planarlaser illumination modules;

[0206]FIG. 6C3 is a schematic representation of the second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.6C1, shown comprising a pair of planar illumination arrays, an area-typeimage formation and detection module, a stationary field of view (FOV)folding mirror, a pair of planar laser illumination beam folding andsweeping mirrors, an image frame grabber, an image data buffer, a decodeimage processor, and a system controller;

[0207]FIG. 6C4 is a schematic representation of the area-type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 5C1, wherein an imaging subsystem having a variable lengthimaging lens, a variable focal distance and variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system during illumination and imagingoperations;

[0208]FIG. 6D is a schematic representation of a presentation typehold-under bar code symbol reading system embodying the PLIIM system ofFIG. 6A;

[0209]FIG. 6D1 is a schematic representation of the PLIIM system of FIG.6A, shown comprising an image formation and detection module, astationary field of view (FOV) folding mirror for folding and projectingthe FOV through a 3-D scanning region, a pair of planar laserillumination arrays, and pair of planar laser beam folding/sweepingmirrors for folding and sweeping the planar laser illumination beams sothat the optical paths of these planar laser illumination beams areoriented in an imaging direction that is coplanar with a section of thefield of view of the image formation and detection module as the planarlaser illumination beams are swept through the 3-D scanning regionduring object illumination and imaging operations;

[0210]FIG. 6D2 is a plan view schematic representation of the PLIIMsystem, taken along line 6D2-6D2 in FIG. 6D 1, showing the spatialextent of the field of view of the image formation and detection modulein the illustrative embodiment of the present invention;

[0211]FIG. 6D3 is an elevated end view schematic representation of thePLIIM system, taken along line 6D3-6D3 in FIG. 6D1, showing the FOV ofthe area image formation and detection module being folded by thestationary FOV folding mirror and projected downwardly through a 3-Dscanning region, and the planar laser illumination beams produced fromthe planar laser illumination arrays being folded and swept so that theoptical paths of these planar laser illumination beams are oriented in adirection that is coplanar with a section of the FOV of the imageformation and detection module as the planar laser illumination beamsare swept through the 3-D scanning region during object illumination andimaging operations;

[0212]FIG. 6D4 is an elevated side view schematic representation of thePLIIM system, taken along line 6D4-6D4 in FIG. 6D1, showing the FOV ofthe area image formation and detection module being folded and projecteddownwardly through the 3-D scanning region, while the planar laserillumination beams are swept through the 3-D scanning region duringobject illumination and imaging operations;

[0213]FIG. 6D5 is an elevated side view of the PLIIM system of FIG. 6D1, showing the spatial limits of the variable field of view (FOV)provided by the area image formation and detection module when imagingthe tallest package moving on a conveyor belt structure must be imaged,as well as the spatial limits of the FOV of the image formation anddetection module when imaging objects having height values close to thesurface height of the conveyor belt structure;

[0214]FIG. 6E1 is a schematic representation of a tenth generalizedembodiment of the PLIIM system of the present invention, wherein a 3-Dfield of view and a pair of planar laser illumination beams arecontrollably steered about a 3-D scanning region;

[0215]FIG. 6E2 is a schematic representation of the PLIIM system shownin FIG. 6E1, shown comprising an area-type image formation and detectionmodule, a pair of planar laser illumination arrays, a pair of x and yaxis field of view (FOV) folding mirrors arranged in relation to theimage formation and detection module, and a pair of x and y axis planarlaser illumination beam sweeping mirrors arranged in relation to thepair of planar laser beam illumination mirrors, such that the planes oflaser illumination are coplanar with a planar section of the 3-D fieldof view of the image formation and detection module as the planar laserillumination beams are automatically scanned across a 3-D region ofspace during object illumination and image detection operations;

[0216]FIG. 6E3 is a schematic representation of the PLIIM system shownin FIG. 6E1, shown, comprising an image formation and detection module,a pair of planar laser illumination arrays, a pair of x and y axis FOVfolding mirrors arranged in relation to the image formation anddetection module, and a pair of x and y axis planar laser illuminationbeam sweeping mirrors arranged in relation to the pair of planar laserbeam illumination mirrors, an image frame grabber, an image data buffer,a decode image processor, and a system controller;

[0217]FIG. 6E4 is a schematic representation showing a portion of thePLIIM system in FIG. 6E1, wherein the 3-D field of view of the imageformation and detection module is steered over the 3-D scanning regionof the system using the x and y axis FOV folding mirrors, working incooperation with the x and y axis planar laser illumination beam foldingmirrors which steer the pair of planar laser illumination beams inaccordance with the principles of the present invention;

[0218]FIG. 7A is a schematic representation of a first illustrativeembodiment of the hybrid holographic/CCD-based PLIIM system of thepresent invention, wherein (i) a pair of planar laser illuminationarrays are used to generate a composite planar laser illumination beamfor illuminating a target object, (ii) a holographic-type cylindricallens is used to collimate the rays of the planar laser illumination beamdown onto the a conveyor belt surface, and (iii) a motor-drivenholographic imaging disc, supporting a plurality of transmission-typevolume holographic optical elements (HOE) having different focallengths, is disposed before a linear (1-D) CCD image detection array,and functions as a variable-type imaging subsystem capable of detectingimages of objects over a large range of object (i.e. working) distanceswhile the planar laser illumination beam illuminates the object;

[0219]FIG. 7B is an elevated side view of the hybridholographic/CCD-based PLIIM system of FIG. 7A, showing the coplanarrelationship between the planar laser illumination beam(s) produced bythe planar laser illumination arrays of the PLIIM system, and thevariable field of view (FOV) produced by the variable holographic-basedfocal length imaging subsystem of the PLIIM system;

[0220]FIG. 8A is a schematic representation of a second illustrativeembodiment of the hybrid holographic/CCD-based PLIIM system of thepresent invention, wherein (i) a pair of planar laser illuminationarrays are used to generate a composite planar laser illumination beamfor illuminating a target object, (ii) a holographic-type cylindricallens is used to collimate the rays of the planar laser illumination beamdown onto the a conveyor belt surface, and (iii) a motor-drivenholographic imaging disc, supporting a plurality of transmission-typevolume holographic optical elements (HOE) having different focallengths, is disposed before an area (2-D) CCD image detection array, andfunctions as a variable-type imaging subsystem capable of detectingimages of objects over a large range of object (i.e. working) distanceswhile the planar laser illumination beam illuminates the object;

[0221]FIG. 8B is an elevated side view of the hybridholographic/CCD-based PLIIM system of FIG. 8A, showing the coplanarrelationship between the planar laser illumination beam(s) produced bythe planar laser illumination arrays of the PLIIM system, and thevariable field of view (FOV) produced by the variable holographic-basedfocal length imaging subsystem of the PLIIM system;

[0222]FIG. 9 is a perspective view of an automated tunnel-type laserscanning package identification and weighing system constructed inaccordance with the first illustrated embodiment of the presentinvention, wherein packages, arranged in a non-singulated or singulatedconfiguration, are transported along a high speed conveyor belt,dimensioned by the LADAR-based imaging, detecting and dimensioningsubsystem of the present invention, weighed by a weighing scale, andidentified by an automatic bar code symbol reading system employing a1-D (i.e. linear) CCD-based scanning array below which a light focusinglens is mounted for imaging bar coded packages transported therebeneathand decode processing to read such bar code symbols in a fully automatedmanner without human intervention;

[0223]FIG. 10 is a schematic block diagram illustrating the subsystemcomponents of the automated tunnel-type package identification andmeasurement system of FIG. 9, namely its LADAR-based package imaging,detecting and dimensioning subsystem, package velocity computationsubsystem, the package-in-tunnel indication subsystem, thepackage-out-of-tunnel subsystem, the package weighing-in-motionsubsystem, the 1-D (i.e. linear) CCD-based bar code symbol readingsubsystem, the data-element queuing, handling and processing subsystem,the input/output port multiplexing subsystem, and the conveyor beltsubsystem integrated together as shown;

[0224]FIG. 11 is a perspective view of an automated tunnel-type laserscanning package identification and weighing system constructed inaccordance with the second illustrated embodiment of the presentinvention, wherein packages, arranged in a non-singulated singulatedconfiguration, are transported along a high speed conveyor belt,dimensioned by the LADAR-based package imaging, detecting anddimensioning subsystem, weighed by the in-weighing subsystem, andidentified PLIIM system of the present invention utilizing low and highresolution CCD image detection arrays for label detection and bar codereading, respectively;

[0225]FIG. 12 is a is a schematic block diagram illustrating thesubsystem components of the automated tunnel-type package identificationand measurement system of FIG. 11, namely its LADAR-based packageimaging, detecting and dimensioning subsystem, package velocitycomputation subsystem, the package-in-tunnel indication subsystem, thepackage-out-of-tunnel subsystem, the package weighing-in-motionsubsystem, the 2-D CCD-based bar code symbol reading subsystem, thedata-element queuing, handling and processing subsystem, theinput/output port multiplexing subsystem, and the conveyor beltsubsystem integrated together as shown;

[0226]FIG. 13 is a schematic representation of a third illustrativeembodiment of the unitary package dimensioning and identification systemof the present invention, embodying the PLIIM subsystem of the presentinvention as well as the laser dimensioning and profiling (LDIP)subsystem within a single housing of compact construction;

[0227]FIG. 14A is a cross-sectional view of the unitary packagedimensioning and identification system of the third illustrativeembodiment, taken along line 14A-14A in FIG. 13, showing the PLIIMsubsystem contained within a first optically isolated compartment formedthe unitary system housing, and the LDIP subsystem contained within asecond optically isolated compartment formed therein, wherein a firstset of spatially registered light transmission apertures are formedthrough the panels of both the first and second cavities to enable thePLIIM system to project its planar laser illumination beams towards atarget object to be illuminated and collect and receive laser returnlight off the illuminated object, and wherein a second set of lighttransmission apertures, optically isolated from the first set of lighttransmission apertures, are formed in the second cavity to enable theLDIP subsystem to project its dual amplitude-modulated laser beamstowards a target object to be dimensioned and profiled, and also tocollect and receive laser return light reflected off the illuminatedtarget object;

[0228]FIG. 14B is a cross-sectional view of the unitary packagedimensioning and identification system of the third illustrativeembodiment, taken along line 14B-14B in FIG. 13, showing the spatiallayout of the various optical and electro-optical components mounted onthe optical bench of the PLIIM subsystem installed within the firstcavity of the system housing;

[0229]FIG. 15 is a schematic representation of the dual cavityconstruction of the system housing used to construct the unitary packagedimensioning and identification system of the third illustrativeembodiment shown in FIGS. 13, 14A and 14B, illustrating the that eachcavity has its own optical bench, and set of light transmissionapertures;

[0230]FIG. 16 is a schematic representation of the unitary (PLIIM-based)package dimensioning and identification system of the third illustrativeembodiment, showing the various information signals generated by theLDIP subsystem, and provided to the camera control (computer)subsystem), and how the camera control computer generates digital cameracontrol signals which are provided to the image formation and detection(IFD subsystem (i.e. “camera”) so that the system can carry out itsdiverse functions in an integrated manner, including (1) capturingdigital images having (i) square pixels (i.e. 1:1 aspect ratio)independent of package height or velocity, (ii) significantly reducedspeckle-noise levels, and (iii) constant image resolution measured indots per inch (DPI) independent of package height or velocity andwithout the use of costly telecentric optics employed by prior artsystems, (2) automatic cropping of captured images so that only regionsof interest reflecting the package or package label are transmitted toeither a image-processing based 1-D or 2-D bar code symbol decoder or anoptical character recognition (OCR) image processor, and (3) automaticimage lifting operations for supporting other package managementoperations carried out by the end-user;

[0231]FIG. 17 is a schematic representation of a fourth illustrativeembodiment of the unitary package dimensioning and identification systemof the present invention, embodying the PLIIM subsystem of the presentinvention as well as the laser dimensioning and profiling (LDIP)subsystem within a single housing of compact construction;

[0232]FIG. 18A is a cross-sectional view of the unitary packagedimensioning and identification system of the fourth illustrativeembodiment, taken along line 18A-18A in FIG. 17, showing the PLIIMsubsystem and its components contained within a first optically isolatedcompartment formed the unitary system housing, and the LDIP subsystemcontained within a second optically isolated compartment formed therein,wherein a first set of spatially registered light transmission aperturesare formed through the panels of both the first and second cavities toenable the PLIIM system to project its planar laser illumination beamstowards a target object to be illuminated and collect and receive laserreturn light off the illuminated object, and wherein a second set oflight transmission apertures, optically isolated from the first set oflight transmission apertures, are formed in the second cavity to enablethe LDIP subsystem to project its dual amplitude-modulated laser beamstowards a target object to be dimensioned and profiled, and also tocollect and receive laser return light reflected off the illuminatedtarget object;

[0233]FIG. 18B is a cross-sectional view of the unitary packagedimensioning and identification system of the third illustrativeembodiment, taken along line 18B-18B in FIG. 17, showing the spatiallayout of the various optical and electro-optical components mounted onthe optical bench of the PLIIM subsystem installed within the firstcavity of the system housing;

[0234]FIG. 18C is a schematic representation of an illustrativeimplementation of the imaging subsystem contained in the image formationand detection (IFD) module employed in the PLIIM system of FIG. 17,shown comprising a stationary lens system mounted before the stationarylinear (CCD-type) image detection array, a first movable lens system forstepped movement relative to the stationary lens system during imagezooming operations, and a second movable lens system for steppedmovements relative to the first movable lens system and the stationarylens system during image focusing operations;

[0235]FIG. 19 a schematic representation of the unitary (PLIIM-based)package dimensioning and identification system of the fourthillustrative embodiment, showing the various information signalsgenerated by the LDIP subsystem, and provided to the camera control(computer) subsystem), and how the camera control computer generatesdigital camera control signals which are provided to the image formationand detection (IFD subsystem (i.e. “camera”) so that the system cancarry out its diverse functions in an integrated manner, including (1)capturing digital images having (i) square pixels (i.e. 1:1 aspectratio) independent of package height or velocity, (ii) significantlyreduced speckle-noise levels, and (iii) constant image resolutionmeasured in dots per inch (DPI) independent of package height orvelocity and without the use of costly telecentric optics employed byprior art systems, (2) automatic cropping of captured images so thatonly regions of interest reflecting the package or package label aretransmitted to either a image-processing based 1-D or 2-D bar codesymbol decoder or an optical character recognition (OCR) imageprocessor, and (3) automatic image lifting operations for supportingother package management operations carried out by the end-user;

[0236]FIG. 20 is a schematic representation of the unitary (PLIIM-based)package dimensioning and identification system of the third and fourthillustrative embodiments shown in FIGS. 13 and 17, showing the use of a“Real-Time” Package Height Profiling And Edge Detection ProcessingModule within the LDIP subsystem to automatically process raw datareceived by the LDIP subsystem and generate, as output, time-stampeddata sets that are transmitted to a Camera Control (Computer) Subsystemwhich automatically processes the received time-stamped data sets andgenerates real-time camera control signals that drive the focus and zoomlens group translators within a high-speed Auto-Focus/Auto-Zoom DigitalCamera Subsystem (i.e. the IFD module) so that the camera subsystemautomatically captures digital images having (1) square pixels (i.e. 1:1aspect ratio) independent of package height or velocity, (2)significantly reduced speckle-noise levels, and (3) constant imageresolution measured in dots per inch (DPI) independent of package heightor velocity;

[0237]FIG. 21 is a flow chart describing the primary data processingoperations that are carried out by the Real-Time Package HeightProfiling And Edge Detection Processing Module within the LDIP subsystememployed in the PLIIM-based systems shown in FIGS. 13 and 17, whereineach sampled row of raw range data collected by the LDIP subsystem isprocessed to produce a data set (containing information data elementsrepresentative of the current time-stamp, the current package height,the current position of the left and right edges of the package edges,and the current package velocity) which is then transmitted to theCamera Control (Computer) Subsystem for processing and generation ofreal-time camera control signals that are transmitted to theAuto-Focus/Auto-Zoom Digital Camera Subsystem;

[0238]FIG. 22 is a flow chart describing the primary data processingoperations that are carried out by the Real-Time Package Edge DetectionProcessing Method performed by the Real-Time Package Height ProfilingAnd Edge Detection Processing Module within the LDIP subsystem ofPLIIM-based systems shown in FIGS. 13 and 17;

[0239]FIG. 23 is a schematic representation of the Real-Time PackageHeight Profiling Method carried out in the flow chart of FIG. 21, andthe Real-Time Package Edge Detection Method carried out in the flowchart of FIG. 22;

[0240]FIGS. 24A and 24B, taken together, set forth a Real-Time CameraControl Process that is carried out within the Camera Control ComputerSubsystem employed within the PLIIM-based systems of FIGS. 13 and 17,wherein the Camera Control (Computer) Subsystem automatically processesthe received time-stamped data sets and generates real-time cameracontrol signals that drive the focus and zoom lens group translatorswithin a high-speed Auto-Focus/Auto-Zoom Digital Camera Subsystem (i.e.the IFD module) so that the camera subsystem automatically capturesdigital images having (1) square pixels (i.e. 1:1 aspect ratio)independent of package height or velocity, (2) significantly reducedspeckle-noise levels, and (3) constant image resolution measured in dotsper inch (DPI) independent of package height or velocity;

[0241]FIG. 25 is a schematic representation of the Package Data Bufferstructure employed by the Real-Time Package Height Profiling And EdgeDetection Processing Module illustrated in FIGS. 20, 21, 22, and 23,wherein each current raw data set received by the Real-Time PackageHeight Profiling And Edge Detection Processing Module is buffered in arow of the Package Data Buffer, and each data element in the raw dataset is assigned a fixed column index and variable row index whichincrements as the raw data set is shifted one index unit as each newincoming raw data set is received into the Package Data Buffer;

[0242]FIG. 26. is a schematic representation of the Camera Pixel DataBuffer structure employed by the Auto-Focus/Auto-Zoom Digital CameraSubsystem shown in FIG. 20, wherein each pixel element in each capturedimage frame is stored in a storage cell of the Camera Pixel Data Buffer,assigned a unique set of pixel indices (ij);

[0243]FIG. 27 is a schematic representation of an exemplary Zoom andFocus Lens Group Position Look-Up Table associated with theAuto-Focus/Auto-Zoom Digital Camera Subsystem used by the Camera Control(Computer) Subsystem of the illustrative embodiment, wherein for a givenpackage height detected by the Real-Time Package Height Profiling AndEdge Detection Processing Module, the Camera Control Computer uses theLook-Up Table to determine the precise positions to which the focus andzoom lens groups must be moved by generating and supplying real-timecamera control signals to the focus and zoom lens group translatorswithin a high-speed Auto-Focus/Auto-Zoom Digital Camera Subsystem (i.e.the IFD module) so that the camera subsystem automatically capturesfocused digital images having (1) square pixels (i.e. 1:1 aspect ratio)independent of package height or velocity, (2) significantly reducedspeckle-noise levels, and (3) constant image resolution measured in dotsper inch (DPI) independent of package height or velocity;

[0244]FIG. 28 is a graphical representation of the focus and zoom lensmovement characteristics associated with the zoom and lens groupsemployed in the illustrative embodiment of the Auto-Focus/Auto-ZoomDigital Camera Subsystem, wherein for a given detected package height,the position of the focus and zoom lens group relative to the Camera'sworking distance is obtained by finding the points along thesecharacteristics at the specified working distance (i.e. detected packageheight);

[0245]FIG. 29 is a schematic representation of an exemplaryPhoto-integration Time Period Look-Up Table associated with CCD imagedetection array employed in the Auto-Focus/Auto-Zoom Digital CameraSubsystem of the PLIIM-based system, wherein for a given detectedpackage height and package velocity, the Camera Control Computer usesthe Look-Up Table to determine the precise photo-integration time periodfor the CCD image detection elements employed within theAuto-Focus/Auto-Zoom Digital Camera Subsystem (i.e. the IFD module) sothat the camera subsystem automatically captures focused digital imageshaving (1) square pixels (i.e. 1:1 aspect ratio) independent of packageheight or velocity, (2) significantly reduced speckle-noise levels, and(3) constant image resolution measured in dots per inch (DPI)independent of package height or velocity;

[0246]FIG. 30 is a schematic representation of the four-sidedtunnel-type package identification and dimensioning (PID) systemconstructed by arranging four PLIIM-based PID units shown in FIGS. 13and 17 about a high-speed package conveyor belt subsystem, wherein theLDIP subsystem in the top PID unit is configured to dimension packagestransported along the belt, while the bottom PID unit is arranged toview packages through a small gap between conveyor belt sections, andall of the PID units are operably connected to the Ethernet control hubof a local area network (LAN);

[0247]FIG. 31 is a schematic system diagram of the tunnel-type systemshown in FIG. 30, embedded within a first-type LAN having a Ethernetcontrol hub; and

[0248]FIG. 32 is a schematic system diagram of the tunnel-type systemshown in FIG. 30, embedded within a second-type LAN having a Ethernetcontrol hub and a Ethernet data switch.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE PRESENTINVENTION

[0249] Referring to the figures in the accompanying Drawings, thepreferred embodiments of the Planar Laser Illumination and (Electronic)Imaging (PLIIM) System of the present invention will be described ingreat detail, wherein like elements will be indicated using likereference numerals.

[0250] Overview of the Planar Laser Illumination and Electronic Imaging(PLIIM) System of the Present Invention

[0251] In accordance with the principles of the present invention, anobject (e.g. a bar coded package, textual materials, graphical indicia,etc.) is illuminated by a substantially planar laser illumination beamhaving substantially-planar spatial distribution characteristics along aplanar direction which passes through the field of view (FOV) of animage formation and detection module (e.g. realized within a CCD-typedigital electronic camera, or a 35 mm optical-film photographic camera),while images of the illuminated object are formed and detected by theimage formation and detection module.

[0252] This inventive principle of coplanar laser illumination and imageformation is embodied in two different classes of the PLIIM, namely: (1)in PLIIM systems shown in FIGS. 1A, 1V1, 2A, 2I1, 3A, and 3J1, whereinthe image formation and detection modules in these systems employlinear-type (1-D) image detection arrays; and (2) in PLIIM systems shownin FIGS. 4A, 5A and 6A, wherein the image formation and detectionmodules in these systems employ area-type (2-D) image detection arrays.Among these illustrative systems, those shown in FIGS. 1A, 2A and 3Aeach produce a planar laser illumination beam that is neither scannednor deflected relative to the system housing during planar laserillumination and image detection operations and thus can be said to use“stationary” planar laser illumination beams to read relatively movingbar code symbol structures and other graphical indicia. Those systemsshown in FIGS. 1V1, 2I1, 3J1, 4A, 5A and 6A, each produce a planar laserillumination beam that is scanned (i.e. deflected) relative to thesystem housing during planar laser illumination and image detectionoperations and thus can be said to use “moving” planar laserillumination beams to read relatively stationary bar code symbolstructures and other graphical indicia.

[0253] In each such system embodiment, it is preferred that each planarlaser illumination beam is focused so that the minimum beam widththereof (e.g. 0.6 mm along its non-spreading direction, as shown in FIG.1I2) occurs at a point or plane which is the farthest or maximum working(i.e. object) distance at which the system is designed to acquire imagesof objects, as best shown in FIG. 1I2. Hereinafter, this aspect of thepresent invention shall be deemed the “Focus Beam At Farthest ObjectDistance (FBAFOD)” principle.

[0254] In the case where a fixed focal length imaging subsystem isemployed in the PLIIM system, the FBAFOD principle helps compensate fordecreases in the power density of the incident planar laser illuminationbeam due to the fact that the width of the planar laser illuminationbeam increases in length for increasing object distances away from theimaging subsystem.

[0255] In the case where a variable focal length (i.e. zoom) imagingsubsystem is employed in the PLIIM system, the FBAFOD principle helpscompensate for (i) decreases in the power density of the incident planarillumination beam due to the fact that the width of the planar laserillumination beam increases in length for increasing object distancesaway from the imaging subsystem, and (ii) any 1/r² type losses thatwould typically occur when using the planar laser planar illuminationbeam of the present invention.

[0256] By virtue of the present invention, scanned objects need only beilluminated along a single plane which is coplanar with a planar sectionof the field of view of the image formation and detection module (e.g.camera) during illumination and imaging operations carried out by thePLIIM system. This enables the use of low-power, light-weight,high-response, ultra-compact, high-efficiency solid-state illuminationproducing devices, such as visible laser diodes (VLDs), to selectivelyilluminate ultra-narrow sections of an object during image formation anddetection operations, in contrast with high-power, low-response,heavy-weight, bulky, low-efficiency lighting equipment (e.g. sodiumvapor lights) required by prior art illumination and image detectionsystems. In addition, the planar laser illumination techniques of thepresent invention enables high-speed modulation of the planar laserillumination beam, and use of simple (i.e. substantially-monochromaticwavelength) lens designs for substantially-monochromatic opticalillumination and image formation and detection operations.

[0257] As will be illustrated in greater detail hereinafter, PLIIMsystems embodying the “planar laser illumination” and “FBAFOD”principles of the present invention can be embodied within a widevariety of bar code symbol reading and scanning systems, as well asoptical character, text, and image recognition systems well known in theart.

[0258] In general, bar code symbol reading systems can be grouped intoat least two general scanner categories, namely: industrial scanners;and point-of-sale (POS) scanners.

[0259] An industrial scanner is a scanner that has been designed for usein a warehouse or shipping application where large numbers of packagesmust be scanned in rapid succession. Industrial scanners includeconveyor-type scanners, and hold-under scanners. These scannercategories will be described in greater detail below.

[0260] Conveyor scanners are designed to scan packages as they move byon a conveyor belt. In general, a minimum of six conveyors (e.g. oneoverhead scanner, four side scanners, and one bottom scanner) arenecessary to obtain complete coverage of the conveyor belt and ensurethat any label will be scanned no matter where on a package it appears.Conveyor scanners can be further grouped into top, side, and bottomscanners which will be briefly summarized below.

[0261] Top scanners are mounted above the conveyor belt and look down atthe tops of packages transported therealong. It might be desirable toangle the scanner's field of view slightly in the direction from whichthe packages approach or that in which they recede depending on theshapes of the packages being scanned. A top scanner generally has lesssevere depth of field and variable focus or dynamic focus requirementscompared to a side scanner as the tops of packages are usually fairlyflat, at least compared to the extreme angles that a side scanner mighthave to encounter during scanning operations.

[0262] Side scanners are mounted beside the conveyor belt and scan thesides of packages transported therealong. It might be desirable to anglethe scanner's field of view slightly in the direction from which thepackages approach or that in which they recede depending on the shapesof the packages being scanned and the range of angles at which thepackages might be rotated.

[0263] Side scanners generally have more severe depth of field andvariable focus or dynamic focus requirements compared to a top scannerbecause of the great range of angles at which the sides of the packagesmay be oriented with respect to the scanner (this assumes that thepackages can have random rotational orientations; if an apparatusupstream on the on the conveyor forces the packages into consistentorientations, the difficulty of the side scanning task is lessened).Because side scanners can accommodate greater variation in objectdistance over the surface of a single target object, side scanners canbe mounted in the usual position of a top scanner for applications inwhich package tops are severely angled.

[0264] Bottom scanners are mounted beneath the conveyor and scans thebottoms of packages by looking up through a break in the belt that iscovered by glass to keep dirt off the scanner. Bottom scanners generallydo not have to be variably or dynamically focused because its workingdistance is roughly constant, assuming that the packages are intended tobe in contact with the conveyor belt under normal operating conditions.However, boxes tend to bounce around as they travel on the belt, andthis behavior can be amplified when a package crosses the break, whereone belt section ends and another begins after a gap of several inches.For this reason, bottom scanners must have a large depth of field toaccommodate these random motions, to which a variable or dynamic focussystem could not react quickly enough.

[0265] Hold-under scanners are designed to scan packages that are pickedup and held underneath it. The package is then manually routed orotherwise handled, perhaps based on the result of the scanningoperation. Hold-under scanners are generally mounted so that its viewingoptics are oriented in downward direction, like a library bar codescanner. Depth of field (DOF) is an important characteristic forhold-under scanners, because the operator will not be able to hold thepackage perfectly still while the image is being acquired.

[0266] Point-of-sale (POS) scanners are typically designed to be used ata retail establishment to determine the price of an item beingpurchased. POS scanners are generally smaller than industrial scannermodels, with more artistic and ergonomic case designs. Small size, lowweight, resistance to damage from accident drops and user comfort areall major design factors for POS scanner. POS scanners include hand-heldscanners, hands-free presentation scanners and combination-type scannerssupporting both hands-on and hands-free modes of operation. Thesescanner categories will be described in greater detail below.

[0267] Hand-held scanners are designed to be picked up by the operatorand aimed at the label to be scanned.

[0268] Hands-free presentation scanners are designed to remainstationary and have the item to be scanned picked up and passed in frontof the scanning device. Presentation scanners can be mounted on counterslooking horizontally, embedded flush with the counter lookingvertically, or partially embedded in the counter looking vertically, buthaving a “tower” portion which rises out above the counter and lookshorizontally to accomplish multiple-sided scanning. If necessary,presentation scanners that are mounted in a counter surface can alsoinclude a scale to measure weights of items.

[0269] Some POS scanners can be used as handheld units or mounted instands to serve as presentation scanners, depending on which is moreconvenient for the operator based on the item that must be scanned.

[0270] Various generalized embodiments of the PLIIM system of thepresent invention will now be described in great detail, and after eachgeneralized embodiment, various applications thereof will be described.

[0271] First Generalized Embodiment of the PLIIM System of the PresentInvention

[0272] The first generalized embodiment of the PLIIM system of thepresent invention 1 is illustrated in FIG. 1A. As shown therein, thePLIIM system 1 comprises: a housing 2 of compact construction; a linear(i.e. 1-dimensional) type image formation and detection (IFD) 3including a 1-D electronic image detection array 3A, and a linear (1-D)imaging subsystem (LIS) 3B having a fixed focal length, a fixed focaldistance, and a fixed field of view (FOV), for forming a 1-D image of anilluminated object 4 located within the fixed focal distance and FOVthereof and projected onto the 1-D image detection array 3A, so that the1-D image detection array 3A can electronically detect the image formedthereon and automatically produce a digital image data setrepresentative of the detected image for subsequent image processing;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B , eachmounted on opposite sides of the IFD module 3, such that each planarlaser illumination array 6A and 6B produces a plane of laser beamillumination 7A, 7B which is disposed substantially coplanar with thefield view of the image formation and detection module 3 during objectillumination and image detection operations carried out by the PLIIMsystem.

[0273] An image formation and detection (IFD) module 3 having an imaginglens with a fixed focal length has a constant angular field of view(FOV); that is, the imaging subsystem can view more of the targetobject's surface as the target object is moved further away from the IFDmodule. A major disadvantage to this type of imaging lens is that theresolution of the image that is acquired, expressed in terms of pixelsor dots per inch (dpi), varies as a function of the distance from thetarget object to the imaging lens. However, a fixed focal length imaginglens is easier and less expensive to design and produce than a zoom-typeimaging lens which will be discussed in detail hereinbelow withreference to FIGS. 3A through 3J4.

[0274] The distance from the imaging lens 3B to the image detecting(i.e. sensing) array 3A is referred to as the image distance. Thedistance from the target object 4 to the imaging lens 3B is called theobject distance. The relationship between the object distance (where theobject resides) and the image distance (at which the image detectionarray is mounted) is a function of the characteristics of the imaginglens, and assuming a thin lens, is determined by the thin (imaging) lensequation (1) defined below in greater detail. Depending on the imagedistance, light reflected from a target object at the object distancewill be brought into sharp focus on the detection array plane. If theimage distance remains constant and the target object is moved to a newobject distance, the imaging lens might not be able to bring the lightreflected off the target object (at this new distance) into sharp focus.An image formation and detection (IFD) module having an imaging lenswith fixed focal distance cannot adjust its image distance to compensatefor a change in the target's object distance; all the component lenselements in the imaging subsystem remain stationary. Therefore, thedepth of field (DOF) of the imaging subsystems alone must be sufficientto accommodate all possible object distances and orientations. Suchbasic optical terms and concepts will be discussed in more formal detailhereinafter with reference to FIGS. 1J1 and 1J6.

[0275] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 3 , and any non-moving FOV and/or planar laser illumination beamfolding mirrors employed in any particular system configurationdescribed herein, are fixedly mounted on an optical bench 8 or chassisso as to prevent any relative motion (which might be caused by vibrationor temperature changes) between: (i) the image forming optics (e.g.imaging lens) within the image formation and detection module 3 and anystationary FOV folding mirrors employed therewith; and (ii) each planarlaser illumination array (i.e. VLD/cylindrical lens assembly) 6A, 6B andany planar laser illumination beam folding mirrors employed in the PLIIMsystem configuration. Preferably, the chassis assembly should providefor easy and secure alignment of all optical components employed in theplanar laser illumination arrays 6A and 6B as well as the imageformation and detection module 3, as well as be easy to manufacture,service and repair. Also, this PLIIM system 1 employs the general“planar laser illumination” and “focus beam at farthest object distance(FBAFOD)” principles described above. Various illustrative embodimentsof this generalized PLIIM system will be described below.

[0276] First Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 1A

[0277] The first illustrative embodiment of the PLIIM system 1A of FIG.1A is shown in FIG. 1B1. As illustrated therein, the field of view ofthe image formation and detection module 3 is folded in the downwardlydirection by a field of view (FOV) folding mirror 9 so that both thefolded field of view 10 and resulting first and second planar laserillumination beams 7A and 7B produced by the planar illumination arrays6A and 6B, respectively, are arranged in a substantially coplanarrelationship during object illumination and image detection operations.One primary advantage of this system design is that it enables aconstruction having an ultra-low height profile suitable, for example,in unitary package identification and dimensioning systems of the typedisclosed in FIGS. 17-22, wherein the image-based bar code symbol readerneeds to installed within a compartment (or cavity) of a housing havingrelatively low height dimensions. Also, in this system design, there isa relatively high degree of freedom provided in where the imageformation and detection module 3 can be mounted on the optical bench ofthe system, thus enabling the field of view (FOV) folding techniquedisclosed in FIG. 1L1 to practiced in a relatively easy manner.

[0278] The PLIIM system 1A illustrated in FIG. 1B1 is shown in greaterdetail in FIG. 1B2. As shown therein, the linear image formation anddetection module 3 is shown comprising an imaging subsystem 3B, and alinear array of photo-electronic detectors 3A realized using high-speedCCD technology (e.g. Dalsa IT-P4 Linear Image Sensors, from Dalsa, Inc.located on the WWW at http://www.dalsa.com). As shown, each planar laserillumination array 6A, 6B comprises a plurality of planar laserillumination modules (PLIMs) 11A through 11F, closely arranged relativeto each other, in a rectilinear fashion. For purposes of clarity, eachPLIM is indicated by reference numeral. As shown in FIGS. 1K1 and 1K2,the relative spacing of each PLIM is such that the spatial intensitydistribution of the individual planar laser beams superimpose andadditively provide a substantially uniform composite spatial intensitydistribution for the entire planar laser illumination array 6A and 6B.

[0279]FIG. 1C is a schematic representation of a single planar laserillumination module (PLIM) 11 used to construct each planar laserillumination array 6A, 6B shown in FIG. 1B2. As shown in FIG. 1C, theplanar laser illumination beam emanates substantially within a singleplane along the direction of beam propagation towards an object to beoptically illuminated.

[0280] As shown in FIG. 1D, the planar laser illumination module of FIG.1C, comprises: a visible laser diode (VLD) 13 supported within anoptical tube or block 14; a light collimating lens 15 supported withinthe optical tube 14; and a cylindrical-type lens element 16 configuredtogether to produce a beam of planar laser illumination 12. As shown inFIG. 1E, a focused laser beam 17 from the focusing lens 15 is directedon the input side of the cylindrical lens element 16, and the producedoutput therefrom is a planar laser illumination beam 12.

[0281] As shown in FIG. 1F, the PLIIM system 1A of FIG. 1A comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofPLMS 11A through 11F, and each PLIM being driven by a VLD driver circuit18 well known in the art; linear-type image formation and detectionmodule 3; field of view (FOV) folding mirror 9, arranged in spatialrelation with the image formation and detection module 3; an image framegrabber 19 operably connected to the linear-type image formation anddetection module 3, for accessing 1-D images (i.e. 1-D digital imagedata sets) therefrom and building a 2-D digital image of the objectbeing illuminated by the planar laser illumination arrays 6A and 6B; animage data buffer (e.g. VRAM) 20 for buffering 2-D images received fromthe image frame grabber 19; a decode image processor 21, operablyconnected to the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer, includingimage-based bar code symbol decoding software such as, for example,SwiftDecode™ Bar Code Decode Software, from Omniplanar, Inc., ofPrinceton, N.J. (http://www.omniplanar.com); and a system controller 22operably connected to the various components within the system forcontrolling the operation thereof in an orchestrated manner.

[0282] Detailed Description of an Exemplary Realization of the PLIIMSystem Shown in FIG. 1B1 Through 1F

[0283] Referring now to FIGS. 1G1 through 1N2, an exemplary realizationof the PLIIM system shown in FIGS. 1B1 through 1F will now be describedin detail below.

[0284] As shown in FIGS. 1G1 and 1G2, the PLIIM system 25 of theillustrative embodiment is contained within a compact housing 26 havingheight, length and width dimensions 45″, 21.7″, and 19.7″ to enable easymounting above a conveyor belt structure or the like. As shown in FIG.1G1, the PLIIM system comprises an image formation and detection module3, a pair of planar laser illumination arrays 6A, 6B, and a stationaryfield of view (FOV) folding structure (e.g. mirror, refractive element,or diffractive element) 9, as shown in FIGS. 1B1 and 1B2. The functionof the FOV folding mirror 9 is to fold the field of view (FOV) of theimage formation and detection module 3 in a direction that is coplanarwith the plane of laser illumination beams 7A and 7B produced by theplanar illumination arrays 6A and 6B respectively. As shown, components6A, 6B, 3 and 9 are fixedly mounted to an optical bench 8 supportedwithin the compact housing 26 by way of metal mounting brackets thatforce the assembled optical components to vibrate together on theoptical bench. In turn, the optical bench is shock mounted to the systemhousing using techniques which absorb and dampen shock forces andvibration. The 1-D CCD imaging array 3A can be realized using a varietyof commercially available high-speed line-scan camera systems such as,for example, the Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com. Notably, imageframe grabber 17, image data buffer (e.g. VRAM) 20, decode imageprocessor 21, and system controller 22 are realized on one or moreprinted circuit (PC) boards contained within a camera and systemelectronic module 27 also mounted on the optical bench, or elsewhere inthe system housing 26

[0285] In general, the linear CCD image detection array (i.e. sensor) 3Ahas a single row of pixels, each of which measures from several μm toseveral tens of μm along each dimension. Square pixels are most common,and most convenient for bar code scanning applications, but differentaspect ratios are available. In principle, a linear CCD detection arraycan see only a small slice of the target object it is imaging at anygiven time. For example, for a linear CCD detection array having 2000pixels, each of which is 10 μm square, the detection array measures 2 cmlong by 10 μm high. If the imaging lens 3B in front of the lineardetection array 3A causes an optical magnification of 10×, then the 2 cmlength of the detection array will be projected onto a 20 cm length ofthe target object. In the other dimension, the 10 μm height of thedetection array becomes only 100 μm when projected onto the target.Since any label to be scanned will typically measure more than a hundredμm or so in each direction, capturing a single image with a linear imagedetection array will be inadequate. Therefore, in practice, the linearimage detection array employed in each of the PLIIM systems shown inFIGS. 1A through 3J6 builds up a complete image of the target object byassembling a series of linear (1-D) images, each of which is taken of adifferent slice of the target object. Therefore, successful use of alinear image detection array in the PLIIM systems shown in FIGS. 1Athrough 3J6 requires relative movement between the target object and thePLIIM system. In general, either the target object is moving and thePLIIM system is stationary, or else the field of view of PLIIM system isswept across a relatively stationary target object, as shown in FIGS.3J1 through 3J4. This makes the linear image detection array a naturalchoice for conveyor scanning applications.

[0286] As shown in FIG. 1G1, the compact housing 26 has a relativelylong light transmission window 28 of elongated dimensions for projectingthe FOV of the image formation and detection module 3 through thehousing towards a predefined region of space outside thereof, withinwhich objects can be illuminated and imaged by the system components onthe optical bench 8. Also, the compact housing 26 has a pair ofrelatively short light transmission apertures 29A and 29B closelydisposed on opposite ends of light transmission window 28, with minimalspacing therebetween, as shown in FIG. 1G1, so that the FOV emergingfrom the housing 26 can spatially overlap in a coplanar manner with thesubstantially planar laser illumination beams projected throughtransmission windows 29A and 29B, as close to transmission window 28 asdesired by the system designer, as shown in FIGS. 1G3 and 1G4. Notably,in some applications, it is desired for such coplanar overlap betweenthe FOV and planar laser illumination beams to occur very close to thelight transmission windows 20, 29A and 29B (i.e. at short optical throwdistances), but in other applications, for such coplanar overlap tooccur at large optical throw distances.

[0287] In either event, each planar laser illumination array 6A and 6Bis optically isolated from the FOV of the image formation and detectionmodule 3. In the preferred embodiment, such optical isolation isachieved by providing a set of opaque wall structures 30A 30B about eachplanar laser illumination array, from the optical bench 8 to its lighttransmission window 29A or 29B, respectively. Such optical isolationstructures prevent the image formation and detection module 3 fromdetecting any laser light transmitted directly from the planar laserillumination arrays 6A, 6B within the interior of the housing. Instead,the image formation and detection module 3 can only receive planar laserillumination that has been reflected off an illuminated object, andfocused through the imaging subsystem of module 3.

[0288] As shown in FIG. 1G3, each planar laser illumination array 6A, 6Bcomprises a plurality of planar laser illumination modules 11A through11F, each individually and adjustably mounted to an L-shaped bracket 32which, in turn, is adjustably mounted to the optical bench. As mentionedabove, each planar laser illumination module 11 must be rotatablyadjustable within its L-shaped bracket so as permit easy yet secureadjustment of the position of each PLIM 11 along a common alignmentplane extending within L-bracket portion 32A thereby permitting precisepositioning of each PLIM relative to the optical axis of the imageformation and detection module 3. Once properly adjusted in terms ofposition on the L-bracket portion 32A, each PLIM can be securely lockedby an allen or like screw threaded into the body of the L-bracketportion 32A. Also, L-bracket portion 32B, supporting a plurality ofPLIMS 11A through 11B, is adjustably mounted to the optical bench 8 andreleasably locked thereto so as to permit precise lateral and/or angularpositioning of the L-bracket 32B relative to the optical axis and FOV ofthe image formation and detection module 3. The function of suchadjustment mechanisms is to enable the intensity distributions of theindividual PLIMs to be additively configured together along asubstantially singular plane, typically having a width or thicknessdimension on the orders of the width and thickness of the spread ordispersed laser beam within each PLIM. When properly adjusted, thecomposite planar laser illumination beam will exhibit substantiallyuniform power density characteristics over the entire working range ofthe PLIIM system, as shown in FIGS. 1K1 and 1K2.

[0289] In FIG. 1G3, the exact position of the individual PLIMs 11Athrough 11F along its L-bracket 32A is indicated relative to the opticalaxis of the imaging lens 3B within the image formation and detectionmodule 3. FIG. 1G3 also illustrates the geometrical limits of eachsubstantially planar laser illumination beam produced by itscorresponding PLIM, measured relative to the folded FOV 10 produced bythe image formation and detection module 3. FIG. 1G4, illustrates how,during object illumination and image detection operations, the FOV ofthe image formation and detection module 3 is first folded by FOVfolding mirror 19, and then arranged in a spatially overlappingrelationship with the resulting/composite planar laser illuminationbeams in a coplanar manner in accordance with the principles of thepresent invention.

[0290] Notably, the PLIIM system of FIG. 1G1 has an image formation anddetection module with an imaging subsystem having a fixed focal distancelens and a fixed focusing mechanism. Thus, such a system is best used ineither hand-held scanning applications, and/or bottom scanningapplications where bar code symbols and other structures can be expectedto appear at a particular distance from the imaging subsystem. In FIG.1G5, the spatial limits for the FOV of the image formation and detectionmodule are shown for two different scanning conditions, namely: whenimaging the tallest package moving on a conveyor belt structure; andwhen imaging objects having height values close to the surface of theconveyor belt structure. In a PLIIM system having a fixed focal distancelens and a fixed focusing mechanism, the PLIIM system would be capableof imaging objects under one of the two conditions indicated above, butnot under both conditions. In a PLIIM system having a fixed focal lengthlens and a variable focusing mechanism, the system can adjust to imageobjects under either of these two conditions.

[0291] In the PLIIM system of FIG. 1G1, special measures are undertakento ensure that (i) a minimum safe distance is maintained between theVLDs in each PLIM and the user's eyes, and (ii) the planar laserillumination beam is prevented from directly scattering into the FOV ofthe image formation and detection module, from within the systemhousing, during object illumination and imaging operations. Condition(i) above can be achieved by using a light shield 32A or 32B shown inFIGS. 1G6 and 1G7, respectively, whereas condition (ii) above can beachieved by ensuring that the planar laser illumination beam from thePLIAs and the field of view (FOV) of the imaging lens (in the IFDmodule) do not spatially overlap on any optical surfaces residing withinthe PLIIM system. Instead, the planar laser illumination beams arepermitted to spatially overlap with the FOV of the imaging lens onlyoutside of the system housing, measured at a particular point beyond thelight transmission window 28, through which the FOV 10 is projected tothe exterior of the system housing, to perform object imagingoperations.

[0292] Detailed Description of the Planar Laser Illumination Modules(PLIMs) Employed in the Planar Laser Illumination Arrays (PLIAs) of theIllustrative Embodiments

[0293] Referring now to FIGS. 1G8 through 1I2, the construction of eachPLIM 14 and 15 used in the planar laser illumination arrays (PLIAs) willnow be described in greater detail below.

[0294] As shown in FIG. 1G8, each planar laser illumination array (PLIA)6A, 6B employed in the PLIIM system of FIG. 1G1, comprises an array ofplanar laser illumination modules (PLIMs) 11 mounted on the L-bracketstructure 32, as described hereinabove. As shown in FIGS. 1G9 through1G11, each PLIM of the illustrative embodiment disclosed hereincomprises an assembly of subcomponents: a VLD mounting block 14 having atubular geometry with a hollow central bore 14A formed entirelytherethrough, and a v-shaped notch 14B formed on one end thereof; avisible laser diode (VLD) 13 (e.g. Mitsubishi ML1XX6 Series high-power658 nm AlGaInP semiconductor laser) axially mounted at the end of theVLD mounting block, opposite the v-shaped notch 14B, so that the laserbeam produced from the VLD 13 is aligned substantially along the centralaxis of the central bore 14A; a cylindrical lens 16, made of opticalglass (e.g. borosilicate) or plastic having the optical characteristicsspecified, for example, in FIGS. 1G1 and 1G2, and fixedly mounted withinthe V-shaped notch 14B at the end of the VLD mounting block 14, using anoptical cement or other lens fastening means, so that the central axisof the cylindrical lens 16 is oriented substantially perpendicular tothe optical axis of the central bore 14A; and a focusing lens 15, madeof central glass (e.g. borosilicate) or plastic having the opticalcharacteristics shown, for example, in FIGS. 1H and 1H2, mounted withinthe central bore 14A of the VLD mounting block 14 so that the opticalaxis of the focusing lens 15 is substantially aligned with the centralaxis of the bore 14A, and located at a distance from the VLD whichcauses the laser beam output from the VLD 13 to be converging in thedirection of the cylindrical lens 16. Notably, the function of thecylindrical lens 16 is to disperse (i.e. spread) the focused laser beamfrom focusing lens 15 along the plane in which the cylindrical lens 16has curvature, as shown in FIG. 1I1 while the characteristics of theplanar laser illumination beam (PLIB) in the direction transverse to thepropagation plane are determined by the focal length of the focusinglens 15, as illustrated in FIGS. 1I1 and 1I2.

[0295] As will be described in greater detail hereinafter, the focallength of the focusing lens 15 within each PLIM hereof is preferablyselected so that the substantially planar laser illumination beamproduced from the cylindrical lens 16 is focused at the farthest objectdistance in the field of view of the image formation and detectionmodule 3, as shown in FIG. 1I2, in accordance with the “FBAFOD”principle of the present invention. As shown in the exemplary embodimentof FIGS. 1I1 and 1I2, wherein each PLIM has maximum object distance ofabout 61 inches (i.e. 155 centimeters), and the cross-sectionaldimension of the planar laser illumination beam emerging from thecylindrical lens 16, in the non-spreading (height) direction, orientednormal to the propagation plane as defined above, is about 0.15centimeters and ultimately focused down to about 0.06 centimeters at themaximal object distance (i.e. the farthest distance at which the systemis designed to capture images). The behavior of the height dimension ofthe planar laser illumination beam is determined by the focal length ofthe focusing lens 15 embodied within the PLIM. Proper selection of thefocal length of the focusing lens 15 in each PLIM and the distancebetween the VLD 13 and the focusing lens 15B indicated by reference No.(D), can be determined using the thin lens equation (1) below and themaximum object distance required by the PLIIM system, typicallyspecified by the end-user. As will be explained in greater detailhereinbelow, this preferred method of VLD focusing helps compensate fordecreases in the power density of the incident planar laser illuminationbeam (on target objects) due to the fact that the width of the planarlaser illumination beam increases in length for increasing distancesaway from the imaging subsystem (i.e. object distances).

[0296] After specifying the optical components for each PLIM, andcompleting the assembly thereof as described above, each PLIM isadjustably mounted to the L bracket position 32A by way of a set ofmounting/adjustment screws turned through fine-threaded mounting holesformed thereon. In FIG. 1G10, the plurality of PLIMs 11A through 11F areshown adjustably mounted on the L-bracket at positions and angularorientations which ensure substantially uniform power densitycharacteristics in both the near and far field portions of the planarlaser illumination field produced by planar laser illumination arrays(PLIAs) 6A and 6B cooperating together in accordance with the principlesof the present invention. Notably, the relative positions of the PLIMsindicated in FIG. 1G9 were determined for a particular set of acommercial VLDs 13 used in the illustrative embodiment of the presentinvention, and, as the output beam characteristics will vary for eachcommercial VLD used in constructing each such PLIM, it is thereforeunderstood that each such PLIM may need to be mounted at differentrelative positions on the L-bracket of the planar laser illuminationarray to obtain, from the resulting system, substantially uniform powerdensity characteristics at both near and far regions of the planar laserillumination field produced thereby.

[0297] While a refractive-type cylindrical lens element 16 has beenshown mounted at the end of each PLIM of the illustrative embodiments,it is understood each cylindrical lens element can be realized usingrefractive, reflective and/or diffractive technology and devices,including reflection and transmission type holographic optical elements(HOEs) well know in the art and described in detail in publishedInternational Application No. WO 99/57579 Nov. 11, 1999 [108-010PCT000],incorporated herein by reference. The only requirement of the opticalelement mounted at the end of each PLIM is that it has sufficientoptical properties to convert a focusing laser beam transmittedtherethrough, into a laser beam which expands or otherwise spreads outonly along a single plane of propagation, while the laser beam issubstantially unaltered (i.e. neither compressed or expanded) in thedirection normal to the propagation plane. As used hereinafter and inthe claims, the terms “cylindrical lens”, “cylindrical lens element” and“cylindrical optical element (COE)” shall be deemed to embrace all suchalternative embodiments of this aspect of the present invention.

[0298] Detailed Description of the Image Formation and Detection ModuleEmployed in the PLIIM System of the First Generalized Embodiment of thePresent Invention

[0299] In FIG. 1J1, there is shown a geometrical model (based on thethin lens equation) for the simple imaging subsystem 3B employed in theimage formation and detection module 3 in the PLIIM system of the firstgeneralized embodiment shown in FIG. 1A. As shown in FIG. 11J1, thissimple imaging system 3B consists of a source of illumination (e.g.laser light reflected off a target object) and an imaging lens. Theillumination source is at an object distance r₀ measured from the centerof the imaging lens. In FIG. 1J1, some representative rays of light havebeen traced from the source to the front lens surface. The imaging lensis considered to be of the converging type which, for ordinary operatingconditions, focuses the incident rays from the illumination source toform an image which is located at an image distance r_(i) on theopposite side of the imaging lens. In FIG. 1J1, some representative rayshave also been traced from the back lens surface to the image. Theimaging lens itself is characterized by a focal length f, the definitionof which will be discussed in greater detail hereinbelow.

[0300] For the purpose of simplifying the mathematical analysis, theimaging lens is considered to be a thin lens, that is, idealized to asingle surface with no thickness. The parameters f, r₀ and r_(i), all ofwhich have units of length, are related by the “thin lens” equation (1)set forth below: $\begin{matrix}{\frac{1}{f} = {\frac{1}{r_{0}} + \frac{1}{r_{i}}}} & (1)\end{matrix}$

[0301] This equation may be solved for the image distance, which yieldsexpression (2) $\begin{matrix}{r_{i} = \frac{{fr}_{0}}{r_{0} - f}} & (2)\end{matrix}$

[0302] If the object distance r₀ goes to infinity, then expression (2)reduces to r_(i)=f. length of the imaging lens is the image distance atwhich light incident on the lens from an infinitely distant object willbe focused. Once f is known, the image distance for light from any otherobject distance can be determined using (2).

[0303] Field of View of The Imaging Lens and Resolution of The DetectedImage

[0304] The basic characteristics of an image detected by the IFD module3 hereof may be determined using the technique of ray tracing, in whichrepresentative rays of light are drawn from the source through theimaging lens and to the image. Such ray tracing is shown in FIG. 1J2. Abasic rule of ray tracing is that a ray from the illumination sourcethat passes through the center of the imaging lens continues undeviatedto the image. That is, a ray that passes through the center of theimaging lens is not refracted. Thus, the size of the field of view (FOV)of the imaging lens may be determined by tracing rays (backwards) fromthe edges of the image detection/sensing array through the center of theimaging lens and out to the image plane as shown in FIG. 1J2, where d isthe dimension of a pixel, n is the number of pixels on the imagedetector array in this direction, and W is the dimension of the field ofview of the imaging lens. Solving for the FOV dimension W, andsubstituting for r_(i) using expression (2) above yields expression (3)as follows: $\begin{matrix}{W = \frac{{dn}\quad \left( {r_{0} - f} \right)}{f}} & (3)\end{matrix}$

[0305] Now that the size of the field of view is known, the dpiresolution of the image is determined. The dpi resolution of the imageis simply the number of pixels divided by the dimension of the field ofview. Assuming that all the dimensions of the system are measured inmeters, the dots per inch (dpi) resolution of the image is given by theexpression (4) as follows: $\begin{matrix}{{dpi} = \frac{f}{39.37d\quad \left( {r_{0} - f} \right)}} & (4)\end{matrix}$

[0306] Working Distance and Depth of Field of the Imaging Lens

[0307] Light returning to the imaging lens that emanates from objectsurfaces slightly closer to and farther from the imaging lens thanobject distance r₀ will also appear to be in good focus on the image.From a practical standpoint, “good focus” is decided by the decodingsoftware 21 used when the image is too blurry to allow the code to beread (i.e. decoded), then the imaging subsystem is said to be “out offocus”. If the object distance r₀ at which the imaging subsystem isideally focused is known, then it can be calculated theoretically theclosest and farthest “working distances” of the PLIIM system, given byparameters r_(near) and r_(far), respectively, at which the system willstill function. These distance parameters are given by expression (5)and (6) as follows: $\begin{matrix}{r_{near} = \frac{{fr}_{0}\left( {f + {DF}} \right)}{f^{2} + {DFr}_{0}}} & (5) \\{r_{far} = \frac{{fr}_{0}\left( {f - {DF}} \right)}{f^{2} - {DFr}_{0}}} & (6)\end{matrix}$

[0308] where D is the diameter of the largest permissible “circle ofconfusion” on the image detection array. A circle of confusion isessentially the blurred out light that arrives from points at imagedistances other than object distance r₀. When the circle of confusionbecomes too large (when the blurred light spreads out too much) then onewill lose focus. The value of parameter D for a given imaging subsystemis usually estimated from experience during system design, and thendetermined more precisely, if necessary, later through laboratoryexperiment.

[0309] Another optical parameter of interest is the total depth of fieldΔr, which is the difference between distances r_(far) and r_(near); thisparameter is the total distance over which the imaging system will beable to operate when focused at object distance r₀. This opticalparameter may be expressed by equation (7) below: $\begin{matrix}{{\Delta \quad r} = \frac{2{Df}^{\quad 2}{{Fr}_{0}\left( {r_{0} - f} \right)}}{f^{4} - {D^{2}F^{2}r_{0}^{2}}}} & (7)\end{matrix}$

[0310] It should be noted that the parameter Δr is generally notsymmetric about r₀; the depth of field usually extends farther towardsinfinity from the ideal focal distance than it does back towards theimaging lens.

[0311] Modeling a Fixed Focal Length Imaging Subsystem Used in the ImageFormation and Detection Module of the Present Invention

[0312] A typical imaging (i.e. camera) lens used to construct a fixedfocal-length image formation and detection module of the presentinvention might typically consist of three to fifteen or more individualoptical elements contained within a common barrel structure. Theinherent complexity of such an optical module prevents its performancefrom being described very accurately using a “thin lens analysis”,described above by equation (1). However, the results of a thin lensanalysis can be used as a useful guide when choosing an imaging lens fora particular PLIIM system application.

[0313] A typical imaging lens can focus light (illumination) originatinganywhere from an infinite distance away, to a few feet away. However,regardless of the origin of such illumination, its rays must be broughtto a sharp focus at exactly the same location (e.g. the film plane orimage detector), which (in an ordinary camera) does not move. At firstglance, this requirement may appear unusual because the thin lensequation (1) above states that the image distance at which light isfocused through a thin lens is a function of the object distance atwhich the light originates, as shown in FIG. 1J3. Thus, it would appearthat the position of the image detector would depend on the distance atwhich the object being imaged is located. An imaging subsystem having avariable focal distance lens assembly avoids this difficulty becauseseveral of its lens elements are capable of movement relative to theothers. For a fixed focal length imaging lens, the leading lenselement(s) can move back and forth a short distance, usuallyaccomplished by the rotation of a helical barrel element which convertsrotational motion into purely linear motion of the lens elements. Thismotion has the effect of changing the image distance to compensate for achange in object distance, allowing the image detector to remain inplace, as shown in the schematic optical diagram of FIG. 1J4.

[0314] Modeling a Variable Focal Length (Zoom) Imaging Lens Used in theImage Formation and Detection Module of the Present Invention

[0315] As shown in FIG. 1J5, a variable focal length (zoom) imagingsubsystem has an additional level of internal complexity. A zoom-typeimaging subsystem is capable of changing its focal length over a givenrange; a longer focal length produces a smaller field of view at a givenobject distance. Consider the case where the PLIIM system needs toilluminate and image a certain object over a range of object distances,but requires the illuminated object to appear the same size in allacquired images. When the object is far away, the PLIIM system willgenerate control signals that select a long focal length, causing thefield of view to shrink (to compensate for the decrease in apparent sizeof the object due to distance). When the object is close, the PLIIMsystem will generate control signals that select a shorter focal length,which widens the field of view and preserves the relative size of theobject. In many bar code scanning applications, a zoom-type imagingsubsystem in the PLIIM system (as shown in FIGS. 3A through 3J5) ensuresthat all acquired images of bar code symbols have the same dpi imageresolution regardless of the position of the bar code symbol within theobject distance of the PLIIM system.

[0316] As shown in FIG. 1J5, a zoom-type imaging subsystem has twogroups of lens elements which are able to undergo relative motion. Theleading lens elements are moved to achieve focus in the same way as fora fixed focal length lens. Also, there is a group of lenses in themiddle of the barrel which move back and forth to achieve the zoom, thatis, to change the effective focal length of all the lens elements actingtogether.

[0317] Several Techniques for Accommodating the Field of View (FOV) of aPLIIM System to Particular End-User Environments

[0318] In many applications, a PLIIM system of the present invention mayinclude an imaging subsystem with a very long focal length imaging lens(assembly), and this PLIIM system must be installed in end-userenvironments having a substantially shorter object distance range,and/or field of view (FOV) requirements or the like. Such problems canexist for PLIIM systems employing either fixed or variable focal lengthimaging subsystems. To accommodate a particular PLIIM system forinstallation in such environments, three different techniquesillustrated in FIGS. 1K1-1K2, 1L1 and 1L2 can be used.

[0319] In FIGS. 1K1 and 1K2, the focal length of the imaging lens 3B canbe fixed and set at the factory to produce a field of view havingspecified geometrical characteristics for particular applications. InFIG. K1, the focal length of the image formation and detection module 3is fixed during the optical design stage so that the fixed field of view(FOV) thereof substantially matches the scan field width measured at thetop of the scan field, and thereafter overshoots the scan field andextends on down to the plane of the conveyor belt 34. In this FOVarrangement, the dpi image resolution will be greater for packageshaving a higher height profile above the conveyor belt, and less forenvelope-type packages with low height profiles. In FIG. 1K2, the focallength of the image formation and detection module 3 is fixed during theoptical design stage so that the fixed field of view thereofsubstantially matches the plane slightly above the conveyor belt 34where envelope-type packages are transported. In this FOV arrangement,the dpi image resolution will be maximized for envelope-type packageswhich are expected to be transported along the conveyor belt structure,and this system will be unable to read bar codes on packages having aheight-profile exceeding the low-profile scanning field of the system.

[0320] In FIG. 1L, a FOV beam folding mirror arrangement is used to foldthe optical path of the imaging subsystem within the interior of thesystem housing so that the FOV emerging from the system housing hasgeometrical characteristics that match the scanning application at hand.As shown, this technique involves mounting a plurality of FOV foldingmirrors 9A through 9E on the optical bench of the PLIIM system to bouncethe FOV of the imaging subsystem 3B back and forth before the FOVemerges from the system housing. Using this technique, when the FOVemerges from the system housing, it will have expanded to a sizeappropriate for covering the entire scan field of the system. Thistechnique is easier to practice with image formation and detectionmodules having linear image detectors, for which the FOV folding mirrorsonly have to expand in one direction as the distance from the imagingsubsystem increases. In FIG. 1L, this direction of FOV expansion occursin the direction perpendicular to the page. In the case of area-typePLIIM systems, as shown in FIGS. 4A through 6F4, the FOV folding mirrorshave to accommodate a 3-D FOV which expands in two directions. Thus aninternal folding path is easier to arrange for linear-type PLIIMsystems.

[0321] In FIG. 1L2, the fixed field of view of an imaging subsystem isexpanded across a working space (e.g. conveyor belt structure) by usinga motor 35 to controllably rotate the FOV 10 during object illuminationand imaging operations. When designing a linear-type PLIIM system forindustrial scanning applications, wherein the focal length of theimaging subsystem is fixed, a higher dpi image resolution willoccasionally be required. This implies using a longer focal lengthimaging lens, which produces a narrower FOV and thus higher dpi imageresolution. However, in many applications, the image formation anddetection module in the PLIIM system cannot be physically located farenough away from the conveyor belt (and within the system housing) toenable the narrow FOV to cover the entire scanning field of the system.In this case, a FOV folding mirror 9F can be made to rotate, relative tostationary for folding mirror 9G, in order to sweep the linear FOV fromside to side over the entire width of the conveyor belt, depending onwhere the bar coded package is located. Ideally, this rotating FOVfolding mirror 9F would have only two mirror positions, but this willdepend on how small the FOV is at the top of the scan field. Therotating FOV folding mirror can be driven by motor 35 operated under thecontrol of the system controller 22, as described herein.

[0322] Method of Adjusting the Focal Characteristics of the Planar LaserIllumination Beams Generated by Planar Laser Illumination Arrays Used inConjunction with Image Formation and Detection Modules Employing FixedFocal Length Imaging Lenses

[0323] In the case of a fixed focal length camera lens, the planar laserillumination beam 7A, 7B is focused at the farthest possible objectdistance in the PLIIM system. In the case of fixed focal length imaginglens, this focus control technique of the present invention is notemployed to compensate for decrease in the power density of thereflected laser beam as a function of 1/r² distance from the imagingsubsystem, but rather to compensate for a decrease in power density ofthe planar laser illumination beam on the target object due to anincrease in object distance away from the imaging subsystem.

[0324] It can be shown that laser return light that is reflected by thetarget object (and measured/detected at any arbitrary point in space)decreases in intensity as the inverse square of the object distance. Inthe PLIIM system of the present invention, the relevant decrease inintensity is not related to such “inverse square” law decreases, butrather to the fact that the width of the planar laser illumination beamincreases as the object distance increases. This“beam-width/object-distance” law decrease in light intensity will bedescribed in greater detail below.

[0325] Using a thin lens analysis of the imaging subsystem, it can beshown that when any form of illumination having a uniform power densityE₀ (i.e. power per unit area) is directed incident on a target objectsurface and the reflected laser illumination from the illuminated objectis imaged through an imaging lens having a fixed focal length f andf-stop F, the power density E_(pix) (measured at the pixel of the imagedetection array and expressed as a function of the object distance r) isprovided by the expression (8) set forth below: $\begin{matrix}{E_{pix} = {\frac{E_{0}}{8F}\left( {1 - \frac{f}{r}} \right)^{2}}} & (8)\end{matrix}$

[0326]FIG. 1M1 shows a plot of pixel power density E_(pix) vs. objectdistance r calculated using the arbitrary but reasonable values E₀=1W/m², f=80 mm and F=4.5. This plot demonstrates that, in acounter-intuitive manner, the power density at the pixel (and thereforethe power incident on the pixel, as its area remains constant) actuallyincreases as the object distance increases. Careful analysis explainsthis particular optical phenomenon by the fact that the field of view ofeach pixel on the image detection array increases slightly faster withincreases in object distances than would be necessary to compensate forthe 1/r² return light losses. A more analytical explanation is providedbelow.

[0327] The width of the planar laser illumination beam increases asobject distance r increases. At increasing object distances, theconstant output power from the VLD in each planar laser illuminationmodule (PLIM) is spread out over a longer beam width, and therefore thepower density at any point along the laser beam width decreases. Tocompensate for this phenomenon, the planar laser illumination beam ofthe present invention is focused at the farthest object distance so thatthe height of the planar laser illumination beam becomes smaller as theobject distance increases; as the height of the planar laserillumination beam becomes narrower towards the farthest object distance,the laser beam power density increases at any point along the width ofthe planar laser illumination beam. The decrease in laser beam powerdensity due to an increase in planar laser beam width and the increasein power density due to a decrease in planar laser beam height, roughlycancel each other out, resulting in a power density which either remainsapproximately constant or increases as a function of increasing objectdistance, as the application at hand may require.

[0328] When the laser beam is fanned (i.e. spread) out into asubstantially planar laser illumination beam by the cylindrical lenselement employed within each PLIM in the PLIIM system, the total outputpower in the planar laser illumination beam is distributed along thewidth of the beam in a roughly Gaussian distribution, as shown in thepower vs. position plot of FIG. 1M2. Notably, this plot was constructedusing actual data gathered with a planar laser illumination beam focusedat the farthest object distance in the PLIIM system. For comparisonpurposes, the data points and a Gaussian curve fit are shown for theplanar laser beam widths taken at the nearest and farthest objectdistances. To avoid having to consider two dimensions simultaneously(i.e. left-to-right along the planar laser beam width dimension andnear-to-far through the object distance dimension), the discussion belowwill assume that only a single pixel is under consideration, and thatthis pixel views the target object at the center of the planar laserbeam width.

[0329] For a fixed focal length imaging lens, the width L of the planarlaser beam is a function of the fan/spread angle θ induced by (i) thecylindrical lens element in the PLIM and (ii) the object distance r, asdefined by the following expression (9): $\begin{matrix}{L = {2r\quad \tan \frac{\theta}{2}}} & (9)\end{matrix}$

[0330]FIG. 1M3 shows a plot of beam width length L versus objectdistance r calculated using θ=50°, demonstrating the planar laser beamwidth increases as a function of increasing object distance.

[0331] The height parameter of the planar laser illumination beam “h” iscontrolled by adjusting the focusing lens 15 between the visible laserdiode (VLD) 13 and the cylindrical lens 16, shown in FIGS. 1I1 and 1I2.FIG. 1M4 shows a typical plot of planar laser beam height h vs. imagedistance r for a planar laser illumination beam focused at the farthestobject distance in accordance with the principles of the presentinvention. As shown in FIG. 1M4, the height dimension of the planarlaser beam decreases as a function of increasing object distance.

[0332] Assuming a reasonable total laser power output of 20 mW from theVLD 13 in each PLIM 11, the values shown in the plots of FIGS. 1M3 and1M4 can be used to determine the power density E₀ of the planar laserbeam at the center of its beam width, expressed as a function of objectdistance. This measure, plotted in FIG. 1N, demonstrates that the use ofthe laser beam focusing technique of the present invention, wherein theheight of the planar laser illumination beam is decreased as the objectdistance increases, compensates for the increase in beam width in theplanar laser illumination beam, which occurs for an increase in objectdistance. This yields a laser beam power density on the target objectwhich increases as a function of increasing object distance over asubstantial portion of the object distance range of the PLIIM system.

[0333] Finally, the power density E₀ plot shown in FIG. 1N can be usedwith expression (1) above to determine the power density on the pixel,E_(pix). This E_(pix) plot is shown in FIG. 10. For comparison purposes,the plot obtained when using the beam focusing method of the presentinvention is plotted in FIG. 1O against a “reference” power density plotE_(pix) which is obtained when focusing the laser beam at infinity,using a collimating lens (rather than a focusing lens 15) disposed afterthe VLD 13, to produce a collimated-type planar laser illumination beamhaving a constant beam height of 1 mm over the entire portion of theobject distance range of the system. Notably, however, thisnon-preferred beam collimating technique, selected as the reference plotin FIG. 1O, does not compensate for the above-described effectsassociated with an increase in planar laser beam width as a function ofobject distance. Consequently, when using this non-preferred beamfocusing technique, the power density of the planar laser illuminationbeam produced by each PLIM decreases as a function of increasing objectdistance.

[0334] Therefore, in summary, where a fixed or variable focal lengthimaging subsystem is employed in the PLIIM system hereof, the planarlaser beam focusing technique of the present invention described abovehelps compensate for decreases in the power density of the incidentplanar illumination beam due to the fact that the width of the planarlaser illumination beam increases for increasing object distances awayfrom the imaging subsystem.

[0335] Producing a Composite Planar Laser Illumination Beam HavingSubstantially Uniform Power Density Characteristics in Near and FarFields By Additively Combining the Individual Gaussian Power DensityDistributions of Planar Laser Illumination Beams Produced by PlanarLaser Illumination Beam Modules (PLIMS) in Planar Laser IlluminationArrays (PLIAs)

[0336] Having described the best known method of focusing the planarlaser illumination beam produced by each VLD in each PLIM in the PLIIMsystem hereof, it is appropriate at this juncture to describe how theindividual Gaussian power density distributions of the planar laserillumination beams produced a PLIA 6A, 6B are additively combined toproduce a composite planar laser illumination beam having substantiallyuniform power density characteristics in near and far fields, asillustrated in FIGS. 1P1 and 1P2.

[0337] When the laser beam produced from the VLD is transmitted throughthe cylindrical lens, the output beam will be spread out into a laserillumination beam extending in a plane along the direction in which thelens has curvature. The beam size along the axis which corresponds tothe height of the cylindrical lens will be transmitted unchanged. Whenthe planar laser illumination beam is projected onto a target surface,its profile of power versus displacement will have an approximatelyGaussian distribution. In accordance with the principles of the presentinvention, the plurality of VLDs on each side of the IFD module arespaced out and tilted in such a way that their individual power densitydistributions add up to produce a (composite) planar laser illuminationbeam having a magnitude of illumination which is distributedsubstantially uniformly over the entire working depth of the PLIIMsystem (i.e. along the height and width of the composite planar laserillumination beam).

[0338] The actual positions of the PLIMs along each planar laserillumination array are indicated in FIG. 1G3 for the exemplary PLIIMsystem shown in FIGS. 1G1 through 1I2. The mathematical analysis used toanalyze the results of summing up the individual power density functionsof the PLIMs at both near and far working distances was carried outusing the Matlab™ mathematical modeling program by Mathworks, Inc.(http://www.mathworks.com). These results are set forth in the dataplots of FIGS. 1P1 and 1P2. Notably, in these data plots, the totalpower density is greater at the far field of the working range of thePLIIM system. This is because the VLDs in the PLIMs are focused toachieve minimum beam width thickness at the farthest object distance ofthe system, whereas the beam height is somewhat greater at the nearfield region. Thus, although the far field receives less illuminationpower at any given location, this power is concentrated into a smallerarea, which results in a greater power density within the substantiallyplanar extent of the planar laser illumination beam of the presentinvention.

[0339] When aligning the individual planar laser illumination beams(i.e. planar beam components) produced from each PLIM, it will beimportant to ensure that each such planar laser illumination beamspatially coincides with a section of the FOV of the imaging subsystem,so that the composite planar laser illumination beam produced by theindividual beam components spatially coincides with the FOV of theimaging subsystem throughout the entire working depth of the PLIIMsystem.

[0340] Method of Substantially Reducing the Power Density Spectrum ofSpeckle-Noise at the Linear Image Detection Array by IlluminatingObjects with a Planar Laser Illumination Beam Having Planar LaserIllumination Beam Components that Oscillate Within the Plane Thereof Sothat Multiple Planar Laser Illumination Beam Components RepeatedlyIlluminate the Field of View (FOV) of Each Detection Element in theLinear Image Detection Array During Each Photo-Electronic IntegrationPeriod Thereof

[0341] When detecting images produced by illuminating target objectswith a coherent illumination source as employed in the PLIM of thepresent invention, “speckle” (i.e. substrate or paper) noise isgenerated and detected at the CCD-type electronic image detection array,severely reducing the signal-to-noise (SNR) ratio of the IFD module. Theproblem of speckle levels and patterns in laser scanning systems isanalyzed in the (25 slide) paper entitled “Speckle Noise and LaserScanning Systems” by Sasa Kresic-Juric, Emanuel Marom and LeonardBergstein, of Symbol Technologies, Holtsville, N.Y., published athttp://www.ima.umn.edu/industrial/99-2000/kresic/sld001.htm. However,this publication fails to provide any technically feasible solution thatmight be used in the PLIIM-based systems disclosed herein.

[0342] In the PLIMs disclosed herein, an optical assembly has beenprovided to effectively destroy the spatial and/or temporal coherence ofthe laser illumination sources that are used to generate planar laserillumination beams (PLIBs) within PLIIM-based systems. The manner inwhich the spatial coherence of the illumination sources is destroyed isby creating multiple “virtual” illumination sources that illuminate theobject at different angles, over the photo-integration time period ofthe electronic image detection array used in the IFD module. By thismethod, the optical phase difference between the laser illuminationsources (being detected at a single image detection element over itsphoto-integration period) is changed by a sufficiently large amount(typically a fraction of a wavelength), thereby causing the resultingelectric field at the illumination plane to also change significantly.As the relative phase delays between these virtual illumination sourcesare changing over the photo-integration time period of each imagedetection element, these virtual sources are effectively renderedspatially incoherent with each other. As a result of the coherentaddition of light from such illumination sources a change results in theillumination field (detected at each image detection element in the IFDmodule), thereby reducing a speckle noise pattern observed at the imagedetector. Consequently, image-based bar code symbol decoders and/or OCRprocessors operating on such digital images can be processed withsignificant reductions in error.

[0343] Ideally, the phase altering device should be able to applydifferent phase shifts to the laser illumination beam, on a spatialscale similar to the size of the cylinder lens array elements. There aremany devices that could be used to achieve the desired phase shifting.Such devices include, but are not limited to, moving phase screens,tilting or micro-oscillating mirrors, defocusing elements, deformablemirrors, acousto-optical and electro-optical phase modulators. Each timethe phase of the reimaged illumination sources is changed by asignificant fraction of a wavelength, the speckle noise pattern in thedetected image changes. In order to produce a useful reduction in thestrength of the speckle noise pattern, many such realizations of thespeckle pattern must occur during a single camera frame time (i.e.photo-integration time period of each image detection element). Sincethe speckle noise patterns are roughly uncorrelated, the reduction inspeckle noise amplitude should be proportional to the square root of thenumber of independent virtual laser illumination sources contributing tothe illumination of the target object and formation of the image framethereof. Thus the temporal response time characteristics of the phasemodulator will be set based on several factors including: (1) the degreeof speckle amplitude reduction required by the application at hand; and(2) the photo-integration time period of the image detection elements inthe IFD module, which will be typically set by other considerations(e.g. ensuring that detected pixels are square to satisfy requirementsof image-based bar code symbol decoders and/or OCR processors employedin the PLIIM-based system).

[0344] In FIG. 1G13A, a portion of the cylindrical lens array, realizedas a lenticular screen (with a pitch of 7.5 mm), is shownmicro-oscillated relative to the laser illumination source. Thedistance, D, between the laser source and the cylindrical lens array wasvaried and at each position the effect of lens array motion wasmeasured. The speckle noise pattern varies periodically as the lensarray is translated. The motion required for one cycle of speckle noisevariation was found to be equal to the motion that leads to one wave ofpath difference between the two lenslets in the cylindrical lens array.For a motion of Δx, the apparent angular shift of the (virtual) lasersource as seen by the cylindrical lens array is Δx/D. The path lengthdifference between the centers of the two cylindrical lenslets is then(Δx/D)*P. The speckle noise pattern repeats when this path differenceequals one wave. This test was done with the target at severaldistances. Test results reveal that there is no dependence on thedistance to the target. Tests have also been conducted to reveal thatthe f/# or which portion of the cylindrical lenslet that is illuminated,does not effect the result (i.e. reduction in speckle noise pattern).

[0345] In FIGS. 1G13 through 1G26, various devices and opticalarrangements are disclosed for modulating the phase of the laserillumination sources employed in the PLIMs of the present invention.Also, it is understood that other devices and techniques not shown, maybe used to modify the phase of the wavefront of the composite planarlaser illumination beam so as destroy the spatial coherence of the laserbeam at the image detection plane, and thus mitigate speckle noisepatterns observed thereat. In most of the PLIMs disclosed herein, amicro-oscillating cylindrical lens array is shown to effect the requiredphase modulation, as this technique appears to be a simple and effectiveway to achieve the necessary phase modulation in the composite planarlaser illumination beam to significantly reduce the speckle noisepattern observed at the image detector of the PLIIM-based systems.

[0346] Alternatively, a deformable mirror (DM) may also be disposedalong the optical path of the planar laser illumination beam (e.g.between the cylindrical lens array and the image detection array) tocarry out the speckle noise reduction method of the present invention.In this alternative embodiment, the deformable mirror was driven with asinusoidal signal at approximately 2 kHz. Static testing shows that a 3volt change in drive signal lead to a significant change in the specklenoise pattern observed on the target at the image detector. Since the DMis capable of accepting drive signals of up to 100 V, ideally about 30independent speckle realizations can be produced leading to a reductionin speckle noise amplitude by factor of at least 5. In tests carried outby Applicants, the speckle noise pattern was recorded with a CCD-typeimage detection array having a 30 Hz frame rate.

[0347] In summary, using laser beam processing techniques the abovedescribed, one can expect a reduction in speckle noise amplitude by atleast a factor of four to five.

[0348] Second Alternative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 1A

[0349] In FIG. 1Q1, the second illustrative embodiment of the PLIIMsystem of FIGS. 1A is shown comprising: a 1-D type image formation anddetection (IFD) module 3′, as shown in FIG. 1B1; and a pair of planarlaser illumination arrays 6A and 6B . As shown, these arrays 6A and 6Bare arranged in relation to the image formation and detection module 3so that the field of view thereof is oriented in a direction that iscoplanar with the planes of laser illumination produced by the planarillumination arrays, without using any laser beam or field of viewfolding mirrors. One primary advantage of this system architecture isthat it does not require any laser beam or FOV folding mirrors, employsthe few optical surfaces, and maximizes the return of laser light, andis easy to align. However, it is expected that this system design willmost likely require a system housing having a height dimension which isgreater than the height dimension required by the system design shown inFIG. 1B1.

[0350] As shown in FIG. 1Q2, PLIIM system 1B shown in FIG. 1Q1comprises: planar laser illumination arrays 6A and 6B, each having aplurality of planar laser illumination modules 11A through 11F, and eachplanar laser illumination module being driven by a VLD driver circuit18; linear-type image formation and detection module 3 having an imagingsubsystem with a fixed focal length imaging lens, a fixed focaldistance, and a fixed field of view, and 1-D image detection array (e.g.Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D line imagesformed thereon by the imaging subsystem; an image frame grabber 19operably connected to the linear-type image formation and detectionmodule 3, for accessing 1-D images (i.e. 1-D digital image data sets)therefrom and building a 2-D digital image of the object beingilluminated by the planar laser illumination arrays 6A and 6B; an imagedata buffer (e.g. VRAM) 20 for buffering 2-D images received from theimage frame grabber 19; a decode image processor 21, operably connectedto the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.Preferably, the PLIIM system of FIGS. 1P1 and 102 is realized using thesame or similar construction techniques shown in FIGS. 1G1 through 1I2,and described above.

[0351] Third Alternative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 1A

[0352] In FIG. 1R1, the third illustrative embodiment of the PLIIMsystem of FIGS. 1A, 1C are shown comprising: a 1-D type image formationand detection (IFD) module 3 having a field of view (FOV), as shown inFIG. 1B1; a pair of planar laser illumination arrays 6A and 6B forproducing first and second planar laser illumination beams; and a pairof planar laser beam folding mirrors 37A and 37B arranged. The functionof the planar laser illumination beam folding mirrors 37A and 37B is tofold the optical paths of the first and second planar laser illuminationbeams produced by the pair of planar illumination arrays 37A and 37Bsuch that the field of view (FOV) of the image formation and detectionmodule 3 is aligned in a direction that is coplanar with the planes offirst and second planar laser illumination beams during objectillumination and imaging operations. One notable disadvantage of thissystem architecture is that it requires additional optical surfaceswhich can reduce the intensity of outgoing laser illumination andtherefore reduce slightly the intensity of returned laser illuminationreflected off target objects. Also this system design requires a morecomplicated beam/FOV adjustment scheme, than not using any planar laserillumination beam folding mirrors. This system design can be best usedwhen the planar laser illumination beams do not have large apex anglesto provide sufficiently uniform illumination. In this system embodiment,the PLIMs are mounted on the optical bench as far back as possible fromthe beam folding mirrors, and cylindrical lenses with larger radiuseswill be employed in the design of each PLIM.

[0353] As shown in FIG. 1R2, PLIIM system 1C shown in FIG. 1R1comprises: planar laser illumination arrays 6A and 6B, each having aplurality of planar laser illumination modules 6A through 6B, and eachplanar laser illumination module being driven by a VLD driver circuit18; linear-type image formation and detection module having an imagingsubsystem with a fixed focal length imaging lens, a fixed focaldistance, and a fixed field of view, and 1-D image detection array (e.g.Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D line imagesformed thereon by the imaging subsystem; pair of planar laser beamfolding mirrors 37A and 37B arranged so as to fold the optical paths ofthe first and second planar laser illumination beams produced by thepair of planar illumination arrays 6A and 6B; an image frame grabber 19operably connected to the linear-type image formation and detectionmodule 3, for accessing 1-D images (i.e. 1-D digital image data sets)therefrom and building a 2-D digital image of the object beingilluminated by the planar laser illumination arrays 6A and 6B; an imagedata buffer (e.g. VRAM) 20 for buffering 2-D images received from theimage frame grabber 19; a decode image processor 21, operably connectedto the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.Preferably, the PLIIM system of FIGS. 1Q1 and 1Q2 is realized using thesame or similar construction techniques shown in FIGS. 1G1 through 1I2,and described above.

[0354] Fourth Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 1A

[0355] In FIG. 1S1, the fourth illustrative embodiment of the PLIIMsystem of FIGS. 1A, indicated by reference No. 1D is shown comprising: a1-D type image formation and detection (IFD) module 3 having a field ofview (FOV), as shown in FIG. 1B1; a pair of planar laser illuminationarrays 6A and 6B for producing first and second planar laserillumination beams; a field of view folding mirror 9 for folding thefield of view (FOV) of the image formation and detection module 3 about90 degrees downwardly; and a pair of planar laser beam folding mirrors37A and 37B arranged so as to fold the optical paths of the first andsecond planar laser illumination beams produced by the pair of planarillumination arrays 6A and 6B such that the planes of first and secondplanar laser illumination beams 7A and 7B are in a direction that iscoplanar with the field of view of the image formation and detectionmodule 3. Despite inheriting most of the disadvantages associated withthe system designs shown in FIGS. 1B1 and 1R1, this system architectureallows the length of the system housing to be easily minimized, at theexpense of an increase in the height and width dimensions of the systemhousing.

[0356] As shown in FIG. 1S2, PLIIM system ID shown in FIG. 1S1comprises: planar laser illumination arrays 6A and 6B, each having aplurality of planar laser illumination modules 11A through 11F, and eachplanar laser illumination module being driven by a VLD driver circuit18; linear-type image formation and detection module 3 having an imagingsubsystem with a fixed focal length imaging lens, a fixed focaldistance, and a fixed field of view, and 1-D image detection array (e.g.Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D line imagesformed thereon by the imaging subsystem; a field of view folding mirror9 for folding the field of view (FOV) of the image formation anddetection module 3; a pair of planar laser beam folding mirrors 9 and 3arranged so as to fold the optical paths of the first and second planarlaser illumination beams produced by the pair of planar illuminationarrays 37A and 37B; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner. Preferably, the PLIIM system of FIGS.1S1 and 1S2 is realized using the same or similar constructiontechniques shown in FIGS. 1G1 through 1I2, and described above.

[0357] Applications for the First Generalized Embodiment of the PLIIMSystem of the Present Invention, and the Illustrative EmbodimentsThereof

[0358] Fixed focal distance PLIIM systems shown in FIGS. 1B1 through 1Uare ideal for applications in which there is little variation in theobject distance, such as in a conveyor-type bottom scanner application.As such scanning systems employ a fixed focal length imaging lens, theimage resolution requirements of such applications must be examinedcarefully to determine that the image resolution obtained is suitablefor the intended application. Because the object distance isapproximately constant for a bottom scanner application (i.e. the barcode almost always is illuminated and imaged within the same objectplane), the dpi resolution of acquired images will be approximatelyconstant. As image resolution is not a concern in this type of scanningapplications, variable focal length (zoom) control is unnecessary, and afixed focal length imaging lens should suffice and enable good results.

[0359] A fixed focal distance PLIIM system generally takes up less spacethan a variable or dynamic focus model because more advanced focusingmethods require more complicated optics and electronics, and additionalcomponents such as motors. For this reason, fixed focus PLIIM systemsare good choices for handheld and presentation scanners as indicated inFIG. 1U, wherein space and weight are always critical characteristics.In these applications, however, the object distance can vary over arange from several to a twelve or more inches, and so the designer mustexercise care to ensure that the scanner's depth of field (DOF) alonewill be sufficient to accommodate all possible variations in targetobject distance and orientation. Also, because a fixed focus imagingsubsystem implies a fixed focal length camera lens, the variation inobject distance implies that the dots per inch resolution of the imagewill vary as well. The focal length of the imaging lens must be chosenso that the angular width of the field of view (FOV) is narrow enoughthat the dpi image resolution will not fall below the minimum acceptablevalue anywhere within the range of object distances supported by thePLIIM system.

[0360] Second Generalized Embodiment of the Planar Laser Illuminationand Electronic Imaging System of the Present Invention

[0361] The second generalized embodiment of the PLIIM system of thepresent invention 11 is illustrated in FIGS. 1V1 and 1V2. As shown inFIG. 1V1, the PLIIM system 1′ comprises: a housing 2 of compactconstruction; a linear (i.e. 1-dimensional) type image formation anddetection (IFD) module 3′; and a pair of planar laser illuminationarrays (PLIAs) 6A and 6B mounted on opposite sides of the IFD module 3′.During system operation, laser illumination arrays 6A and 6B eachproduce a moving plane of laser illumination beam 12′ whichsynchronously moves and is disposed substantially coplanar with thefield of view (FOV) of the image formation and detection module 3′, soas to scan a bar code symbol or other graphical structure 4 disposedstationary within a 3-D scanning region.

[0362] As shown in FIGS. 2V2 and 2V3, the PLIIM system of FIG. 2V1comprises: an image formation and detection module 3′ having an imagingsubsystem 3B′ with a fixed focal length imaging lens, a fixed focaldistance, and a fixed field of view, and a 1-D image detection array 3(e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line ScanCamera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D lineimages formed thereon by the imaging subsystem; a field of view sweepingmirror 9 operably connected to a motor mechanism 38 under control ofsystem controller 22, for folding and sweeping the field of view of theimage formation and detection module 3; a pair of planar laserillumination arrays 6A and 6B for producing planar laser illuminationbeams 7A and 7B; a pair of planar laser illumination beamfolding/sweeping mirrors 37A and 37B operably connected to motormechanisms 39A and 39B, respectively, under control of system controller22, for folding and sweeping the planar laser illumination beams 7A and7B, respectively, in synchronism with the FOV being swept by the FOVfolding and sweeping mirror 9; an image frame grabber 19 operablyconnected to the linear-type image formation and detection module 3, foraccessing 1-D images (i.e. 1-D digital image data sets) therefrom andbuilding a 2-D digital image of the object being illuminated by theplanar laser illumination arrays 6A and 6B; an image data buffer (e.g.VRAM) 20 for buffering 2-D images received from the image frame grabber19; a decode image processor 21, operably connected to the image databuffer 20, for carrying out image processing algorithms (including barcode symbol decoding algorithms) and operators on digital images storedwithin the image data buffer; and a system controller 22 operablyconnected to the various components within the system for controllingthe operation thereof in an orchestrated manner.

[0363] An image formation and detection (IFD) module 3 having an imaginglens with a fixed focal length has a constant angular field of view(FOV); that is, the farther the target object is located from the IFDmodule, the larger the projection dimensions of the imaging subsystem'sFOV become on the surface of the target object. A disadvantage to thistype of imaging lens is that the resolution of the image that isacquired, in terms of pixels or dots per inch, varies as a function ofthe distance from the target object to the imaging lens. However, afixed focal length imaging lens is easier and less expensive to designand produce than the alternative, a zoom-type imaging lens which will bediscussed in detail hereinbelow with reference to FIGS. 3A through 3J4.

[0364] Each planar laser illumination module 6A through 6B in PLIIMsystem 1′ is driven by a VLD driver circuit 18 under the systemcontroller 22. Notably, laser illumination beam folding/sweeping mirror37A′ and 38B′, and FOV folding/sweeping mirror 9′ are each rotatablydriven by a motor-driven mechanism 38, 39A, and 39B, respectively,operated under the control of the system controller 22. These threemirror elements can be synchronously moved in a number of differentways. For example, the mirrors 37A′, 37B′ and 9′ can be jointly rotatedtogether under the control of one or more motor-driven mechanisms, oreach mirror element can be driven by a separate driven motor which issynchronously controlled to enable the planar laser illumination beams7A, 7B and FOV 10 to move together in a spatially-coplanar manner duringillumination and detection operations within the PLIIM system.

[0365] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 3, the folding/sweeping FOV mirror 9′, and the planar laserillumination beam folding/sweeping mirrors 37A′ and 37B′ employed inthis generalized system embodiment, are fixedly mounted on an opticalbench or chassis 8 so as to prevent any relative motion (which might becaused by vibration or temperature changes) between: (i) the imageforming optics (e.g. imaging lens) within the image formation anddetection module 3 and the FOV folding/sweeping mirror 9′ employedtherewith; and (ii) each planar laser illumination module (i.e.VLD/cylindrical lens assembly) and the planar laser illumination beamfolding/sweeping mirrors 37A′ and 37B′ employed in this PLIIM systemconfiguration. Preferably, the chassis assembly should provide for easyand secure alignment of all optical components employed in the planarlaser illumination arrays 6A′ and 6B′ , beam folding/sweeping mirrors37A′ and 37B′, the image formation and detection module 3 and FOVfolding/sweeping mirror 9′, as well as be easy to manufacture, serviceand repair. Also, this generalized PLIIM system embodiment 1′ employsthe general “planar laser illumination” and “focus beam at farthestobject distance (FBAFOD)” principles described above.

[0366] Applications for the Second Generalized Embodiment of the PLIIMSystem of the Present Invention

[0367] The fixed focal length PLIIM system shown in FIGS. 1V1-1V3 has a3-D fixed field of view which, while spatially-aligned with a compositeplanar laser illumination beam 12 in a coplanar manner, is automaticallyswept over a 3-D scanning region within which bar code symbols and othergraphical indicia 4 may be illuminated and imaged in accordance with theprinciples of the present invention. As such, this generalizedembodiment of the present invention is ideally suited for use inhand-supportable and hands-free presentation type bar code symbolreaders shown in FIGS. 1V4 and 1V5, respectively, in whichrasterlike-scanning (i.e. up and down) patterns can be used for reading1-D as well as 2-D bar code symbologies such as the PDF 147 symbology.In general, the PLIM system of this generalized embodiment may have anyof the housing form factors disclosed and described in Applicant'scopending US application Ser. No. 09/204,176 entitled filed Dec. 3, 1998and Ser. No. 09/452,976 filed Dec. 2, 1999, and WIPO Publication No. WO00/33239 published Jun. 8, 2000, incorporated herein by reference. Thebeam sweeping technology disclosed in copending application Ser. No.08/931,691 filed Sep. 16, 1997, incorporated herein by reference, can beused to uniformly sweep both the planar laser illumination beam andlinear FOV in a coplanar manner during illumination and imagingoperations.

[0368] Third Generalized Embodiment of the PLIIM System of the PresentInvention

[0369] The third generalized embodiment of the PLIIM system of thepresent invention 40 is illustrated in FIG. 2A. As shown therein, thePLIIM system 40 comprises: a housing 2 of compact construction; a linear(i.e. 1-dimensional) type image formation and detection (IFD) module 3′including a 1-D electronic image detection array 3A, a linear (1-D)imaging subsystem (LIS) 3B′ having a fixed focal length, a variablefocal distance, and a fixed field of view (FOV), for forming a 1-D imageof an illuminated object located within the fixed focal distance and FOVthereof and projected onto the 1-D image detection array 3A, so that the1-D image detection array 3A can electronically detect the image formedthereon and automatically produce a digital image data set 5representative of the detected image for subsequent image processing;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B , eachmounted on opposite sides of the IFD module 3′, such that each planarlaser illumination array 6A and 6B produces a composite plane of laserbeam illumination 12 which is disposed substantially coplanar with thefield view of the image formation and detection module 3′ during objectillumination and image detection operations carried out by the PLIIMsystem.

[0370] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 3′, and any non-moving FOV and/or planar laser illumination beamfolding mirrors employed in any configuration of this generalized systemembodiment, are fixedly mounted on an optical bench or chassis so as toprevent any relative motion (which might be caused by vibration ortemperature changes) between: (i) the image forming optics (e.g. imaginglens) within the image formation and detection module 3′ and anystationary FOV folding mirrors employed therewith; and (ii) each planarlaser illumination module (i.e. VLD/cylindrical lens assembly) and anyplanar laser illumination beam folding mirrors employed in the PLIIMsystem configuration. Preferably, the chassis assembly should providefor easy and secure alignment of all optical components employed in theplanar laser illumination arrays 6A and 6B as well as the imageformation and detection module 3′, as well as be easy to manufacture,service and repair. Also, this generalized PLIIM system embodiment 40employs the general “planar laser illumination” and “focus beam atfarthest object distance (FBAFOD)” principles described above. Variousillustrative embodiments of this generalized PLIIM system will bedescribed below.

[0371] An image formation and detection (IFD) module 3 having an imaginglens with variable focal distance, as employed in the PLIIM system ofFIG. 2A, can adjust its image distance to compensate for a change in thetarget's object distance; thus, at least some of the component lenselements in the imaging subsystem are movable, and the depth of field ofthe imaging subsystems does not limit the ability of the imagingsubsystem to accommodate possible object distances and orientations. Avariable focus imaging subsystem is able to move its components in sucha way as to change the image distance of the imaging lens to compensatefor a change in the target's object distance, thus preserving good focusno matter where the target object might be located. Variable focus canbe accomplished in several ways, namely: by moving lens elements; movingimager detector/sensor; and dynamic focus. Each of these differentmethods will be summarized below for sake of convenience.

[0372] Use of Moving Lens Elements in the Image Formation and DetectionModule

[0373] The imaging subsystem in this generalized PLIIM system embodimentcan employ an imaging lens which is made up of several component lensescontained in a common lens barrel. A variable focus type imaging lenssuch as this can move one or more of its lens elements in order tochange the effective distance between the lens and the image sensor,which remains stationary. This change in the image distance compensatesfor a change in the object distance of the target object and keeps thereturn light in focus. The position at which the focusing lenselement(s) must be in order to image light returning from a targetobject at a given object distance is determined by consulting a lookuptable, which must be constructed ahead of time, either experimentally orby design software, well known in the optics art.

[0374] Use of an Moving Image Detection Array in the Image Formation andDetection Module

[0375] The imaging subsystem in this generalized PLIIM system embodimentcan be constructed so that all the lens elements remain stationary, withthe imaging detector/sensor array being movable relative to the imaginglens so as to change the image distance of the imaging subsystem. Theposition at which the image detector/sensor must be located to imagelight returning from a target at a given object distance is determinedby consulting a lookup table, which must be constructed ahead of time,either experimentally or by design software, well known in the art.

[0376] Use of Dynamic Focal Distance Control in the Image Formation andDetection Module

[0377] The imaging subsystem in this generalized PLIIM system embodimentcan be designed to embody a “dynamic” form of variable focal distance(i.e. focus) control, which is an advanced form of variable focuscontrol. In conventional variable focus control schemes, one focus (i.e.focal distance) setting is established in anticipation of a given targetobject. The object is imaged using that setting, then another setting isselected for the next object image, if necessary. However, depending onthe shape and orientation of the target object, a single target objectmay exhibit enough variation in its distance from the imaging lens tomake it impossible for a single focus setting to acquire a sharp imageof the entire object. In this case, the imaging subsystem must changeits focus setting while the object is being imaged. This adjustment doesnot have to be made continuously; rather, a few discrete focus settingswill generally be sufficient. The exact number will depend on the shapeand orientation of the package being imaged and the depth of field ofthe imaging subsystem used in the IFD module.

[0378] It should be noted that dynamic focus control is only used with alinear image detection/sensor array, as used in the system embodimentsshown in FIGS. 2A through 3J4. The reason for this limitation is quiteclear: an area-type image detection array captures an entire image aftera rapid number of exposures to the planar laser illumination beam, andalthough changing the focus setting of the imaging subsystem might clearup the image in one part of the detector array, it would induce blurringin another region of the image, thus failing to improve the overallquality of the acquired image.

[0379] First Illustrative Embodiment of the PLIIM System Shown in FIG.2A

[0380] The first illustrative embodiment of the PLIIM system of FIG. 2A40A is shown in FIG. 2B1. As illustrated therein, the field of view ofthe image formation and detection module 3′ and the first and secondplanar laser illumination beams 7A and 7B produced by the planarillumination arrays 6A and 6B, respectively, are arranged in asubstantially coplanar relationship during object illumination and imagedetection operations.

[0381] The PLIIM system illustrated in FIG. 2B1 is shown in greaterdetail in FIG. 2B2. As shown therein, the linear image formation anddetection module 3′ is shown comprising an imaging subsystem 3B′, and alinear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images (e.g. 6000 pixels, @60 MHZ scanning rate) formed thereon bythe imaging subsystem 3B′, providing an image resolution of 200 dpi or 8pixels/mm, as the image resolution that results from a fixed focallength imaging lens is the function of the object distance (i.e. thelonger the object distance, the lower the resolution). The imagingsubsystem 3B′ has a fixed focal length imaging lens (e.g. 80 mm Pentaxlens, F4.5), a fixed field of view (FOV), and a variable focal distanceimaging capability (e.g. 36″ total scanning range), and an auto-focusingimage plane with a response time of about 20-30 milliseconds over about5 mm working range.

[0382] As shown, each planar laser illumination array (PLIA) 6A, 6Bcomprises a plurality of planar laser illumination modules (PLIMs) 11Athrough 11F, closely arranged relative to each other, in a rectilinearfashion. As taught hereinabove, the relative spacing and orientation ofeach PLIM 11 is such that the spatial intensity distribution of theindividual planar laser beams 7A, 7B superimpose and additively producecomposite planar laser illumination beam 12 having a substantiallyuniform power density distribution along the widthwise dimensions of thelaser illumination beam, throughout the entire working range of thePLIIM system.

[0383] As shown in FIG. 2C1, the PLIIM system of FIG. 2B1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3A; an image frame grabber 19operably connected to the linear-type image formation and detectionmodule 3A, for accessing 1-D images (i.e. 1-D digital image data sets)therefrom and building a 2-D digital image of the object beingilluminated by the planar laser illumination arrays 6A and 6B; an imagedata buffer (e.g. VRAM) 20 for buffering 2-D images received from theimage frame grabber 19; a decode image processor 21, operably connectedto the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.

[0384]FIG. 2C2 illustrates in greater detail the structure of the IFDmodule 3′ used in the PLIIM system of FIG. 2B1. As shown, the IFD module3′ comprises a variable focus fixed focal length imaging subsystem 3B′and a 1-D image detecting array 3A mounted along an optical bench 30contained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3B′ mounted along theoptical bench before the image detecting array 3A, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis with an optical element translator 3C in response to afirst set of control signals 3E generated by the system controller 22,while the entire group of focal lens elements remain stationary.Alternatively, focal distance control can also be provided by moving theentire group of focal lens elements back and forth with translator 3C inresponse to a first set of control signals 3E generated by the systemcontroller, while the 1-D image detecting array 3A remains stationary.In customized applications, it is possible for the individual lenselements in the group of focusing lens elements 3B′ to be moved inresponse to control signals generated by the system controller 22.Regardless of the approach taken, an IFD module 3′ with variable focusfixed focal length imaging can be realized in a variety of ways, eachbeing embraced by the spirit of the present invention.

[0385] Second Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 2A

[0386] The second illustrative embodiment of the PLIIM system of FIG. 2A40B is shown in FIG. 2D1 comprising: an image formation and detectionmodule 3′ having an imaging subsystem 3B′ with a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view, and alinear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B′; a field of viewfolding mirror 9 for folding the field of view of the image formationand detection module 3′; and a pair of planar laser illumination arrays6A and 6B arranged in relation to the image formation and detectionmodule 3′ such that the field of view thereof folded by the field ofview folding mirror 9 is oriented in a direction that is coplanar withthe composite plane of laser illumination 12 produced by the planarillumination arrays, during object illumination and image detectionoperations, without using any laser beam folding mirrors.

[0387] One primary advantage of this system design is that it enables aconstruction having an ultra-low height profile suitable, for example,in unitary package identification and dimensioning systems of the typedisclosed in FIGS. 17-22, wherein the image-based bar code symbol readerneeds to be installed within a compartment (or cavity) of a housinghaving relatively low height dimensions. Also, in this system design,there is a relatively high degree of freedom provided in where the imageformation and detection module 3′ can be mounted on the optical bench ofthe system, thus enabling the field of view (FOV) folding techniquedisclosed in FIG. 1L1 to be practiced in a relatively easy manner.

[0388] As shown in FIG. 2D2, the PLIIM system of FIG. 2D1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3′; a field of view folding mirror9 for folding the field of view of the image formation and detectionmodule 3′; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3′, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

[0389]FIG. 2D2 illustrates in greater detail the structure of the IFDmodule 3′ used in the PLIIM system of FIG. 2D 1. As shown, the IFDmodule 3′ comprises a variable focus fixed focal length imagingsubsystem 3B′ and a 1-D image detecting array 3A mounted along anoptical bench 3D contained within a common lens barrel (not shown). Theimaging subsystem 3B′ comprises a group of stationary lens elements 3A′mounted along the optical bench before the image detecting array 3A′,and a group of focusing lens elements 3B′ (having a fixed effectivefocal length) mounted along the optical bench in front of the stationarylens elements 3A1. In a non-customized application, focal distancecontrol can be provided by moving the 1-D image detecting array 3A backand forth along the optical axis with a translator 3E in response to afirst set of control signals 3E generated by the system controller 22,while the entire group of focal lens elements remain stationary.Alternatively, focal distance control can also be provided by moving theentire group of focal lens elements 3B′ back and forth with translator3C in response to a first set of control signals 3E generated by thesystem controller 22, while the 1-D image detecting array 3A remainsstationary. In customized applications, it is possible for theindividual lens elements in the group of focusing lens elements 3B′ tobe moved in response to control signals generated by the systemcontroller. Regardless of the approach taken, an IFD module 3′ withvariable focus fixed focal length imaging can be realized in a varietyof ways, each being embraced by the spirit of the present invention.

[0390] Third Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 2A

[0391] The second illustrative embodiment of the PLIIM system of FIG. 2A40C is shown in FIG. 2D1 comprising: an image formation and detectionmodule 3′ having an imaging subsystem 3B′ with a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view, and alinear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B′; a pair ofplanar laser illumination arrays 6A and 6B for producing first andsecond planar laser illumination beams 7A, 7B, and a pair of planarlaser beam folding mirrors 37A and 37B for folding the planes of theplanar laser illumination beams produced by the pair of planarillumination arrays 6A and 6B, in a direction that is coplanar with theplane of the field of view of the image formation and detection duringobject illumination and image detection operations.

[0392] The primary disadvantage of this system architecture is that itrequires additional optical surfaces (i.e. the planar laser beam foldingmirrors) which reduce outgoing laser light and therefore the returnlaser light slightly. Also this embodiment requires a complicatedbeam/FOV adjustment scheme. Thus, this system design can be best usedwhen the planar laser illumination beams do not have large apex anglesto provide sufficiently uniform illumination. Notably, in this systemembodiment, the PLIMs are mounted on the optical bench 8 as far back aspossible from the beam folding mirrors 37A, 37B, and cylindrical lenses16 with larger radiuses will be employed in the design of each PLIM 11.

[0393] As shown in FIG. 2E2, the PLIIM system of FIG. 2E1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3′; a field of view folding mirror9 for folding the field of view of the image formation and detectionmodule 3′; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3A, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

[0394]FIG. 2E3 illustrates in greater detail the structure of the IFDmodule 3′ used in the PLIIM system of FIG. 2E1. As shown, the IFD module3′ comprises a variable focus fixed focal length imaging subsystem 3B′and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3A1 mounted along theoptical bench before the image detecting array 3A, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis in response to a first set of control signals 3Egenerated by the system controller 22, while the entire group of focallens elements 3B′ remain stationary. Alternatively, focal distancecontrol can also be provided by moving the entire group of focal lenselements 3B′ back and forth with translator 3C in response to a firstset of control signals 3E generated by the system controller 22, whilethe 1-D image detecting array 3A remains stationary. In customizedapplications, it is possible for the individual lens elements in thegroup of focusing lens elements 3B′ to be moved in response to controlsignals generated by the system controller 22. Regardless of theapproach taken, an IFD module 3′ with variable focus fixed focal lengthimaging can be realized in a variety of ways, each being embraced by thespirit of the present invention.

[0395] Fourth Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 2A

[0396] The fourth illustrative embodiment of the PLIIM system of FIG. 2A40D is shown in FIG. 2F1 comprising: an image formation and detectionmodule 3′ having an imaging subsystem 3B′ with a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view, and alinear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B′; a field of viewfolding mirror 9 for folding the FOV of the imaging subsystem 3B′; apair of planar laser illumination arrays 6A and 6B for producing firstand second planar laser illumination beams; and a pair of planar laserbeam folding mirrors 37A and 37B arranged in relation to the planarlaser illumination arrays 6A and 6B so as to fold the optical paths ofthe first and second planar laser illumination beams 7A, 7B in adirection that is coplanar with the folded FOV of the image formationand detection module 3′, during object illumination and image detectionoperations.

[0397] As shown in FIG. 2F2, the PLIIM system 40D of FIG. 2F1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11B, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3′; a field of view folding mirror9 for folding the field of view of the image formation and detectionmodule 3′; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3A, for accessing 1 -Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

[0398]FIG. 2F3 illustrates in greater detail the structure of the IFDmodule 3′ used in the PLIIM system of FIG. 2F1. As shown, the IFD module3′ comprises a variable focus fixed focal length imaging subsystem 3B′and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3A1 mounted along theoptical bench 3D before the image detecting array 3A, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis with translator 3C in response to a first set ofcontrol signals 3E generated by the system controller 22, while theentire group of focal lens elements 3B′ remain stationary.Alternatively, focal distance control can also be provided by moving theentire group of focal lens elements 3B′ back and forth with translator3C in response to a first set of control signals 3E generated by thesystem controller 22, while the 1-D image detecting array 3A remainsstationary. In customized applications, it is possible for theindividual lens elements in the group of focusing lens elements 3B′ tobe moved in response to control signals generated by the systemcontroller 22. Regardless of the approach taken, an IFD module withvariable focus fixed focal length imaging can be realized in a varietyof ways, each being embraced by the spirit of the present invention.

[0399] Applications for the Third Generalized Embodiment of the PLIIMSystem of the Present Invention, and the Illustrative EmbodimentsThereof

[0400] As the PLIIM systems shown in FIGS. 2A through 2F3 employ an IFDmodule 3′ having a linear image detecting array and an imaging subsystemhaving variable focus (i.e. focal distance) control, such PLIIM systemsare good candidates for use in a conveyor top scanner application, asshown in FIGS. 2G, as the variation in target object distance can be upto a meter or more (from the imaging subsystem). In general, such objectdistances are too great a range for the depth of field (DOF)characteristics of the imaging subsystem alone to accommodate suchobject distance parameter variations during object illumination andimaging operations. Provision for variable focal distance control isgenerally sufficient for the conveyor top scanner application shown inFIG. 2G, as the demands on the depth of field and variable focus ordynamic focus control characteristics of such PLIIM system are not assevere in the conveyor top scanner application, as they might be in theconveyor side scanner application, also illustrated in FIG. 2G.

[0401] Notably, by adding dynamic focusing functionality to the imagingsubsystem of any of the embodiments shown in FIGS. 2A through 2F3, theresulting PLIIM system becomes appropriate for the conveyorside-scanning application discussed above, where the demands on thedepth of field and variable focus or dynamic focus requirements aregreater compared to a conveyor top scanner application.

[0402] Fourth Generalized Embodiment of the PLIIM System of the PresentInvention

[0403] The fourth generalized embodiment of the PLIIM system 40′ of thepresent invention is illustrated in FIGS. 2I1 and 2I2. As shown in FIG.2I1, the PLIIM system 40′ comprises: a housing 2 of compactconstruction; a linear (i.e. 1-dimensional) type image formation anddetection (IFD) module 3′; and a pair of planar laser illuminationarrays (PLIAs) 6A and 6B mounted on opposite sides of the IFD module 3′.During system operation, laser illumination arrays 6A and 6B eachproduce a moving planar laser illumination beam 12′ which synchronouslymoves and is disposed substantially coplanar with the field of view(FOV) of the image formation and detection module 3′, so as to scan abar code symbol or other graphical structure 4 disposed stationarywithin a 3-D scanning region.

[0404] As shown in FIGS. 2I2 and 2I3, the PLIIM system of FIG. 2I1comprises: an image formation and detection module 3′ having an imagingsubsystem 3B′ with a fixed focal length imaging lens, a variable focaldistance and a fixed field of view, and a linear array ofphoto-electronic detectors 3A realized using CCD technology (e.g.Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D line imagesformed thereon by the imaging subsystem 3B′; a field of view folding andsweeping mirror 9′ for folding and sweeping the field of view 10 of theimage formation and detection module 3′; a pair of planar laserillumination arrays 6A and 6B for producing planar laser illuminationbeams 7A and 7B; a pair of planar laser illumination beam sweepingmirrors 37A′ and 37B′ for folding and sweeping the planar laserillumination beams 7A and 7B, respectively, in synchronism with the FOVbeing swept by the FOV folding and sweeping mirror 9′; an image framegrabber 19 operably connected to the linear-type image formation anddetection module 3A, for accessing 1-D images (i.e. 1-D digital imagedata sets) therefrom and building a 2-D digital image of the objectbeing illuminated by the planar laser illumination arrays 6A and 6B; animage data buffer (e.g. VRAM) 20 for buffering 2-D images received fromthe image frame grabber 19; a decode image processor 21, operablyconnected to the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.As shown in FIG. 2F2, each planar laser illumination module 11A through11F, is driven by a VLD driver circuit 18 under the system controller22. Notably, laser illumination beam folding/sweeping mirrors 37A′ and37B′, and FOV folding/sweeping mirror 9′ are each rotatably driven by amotor-driven mechanism 39A, 39B, 38, respectively, operated under thecontrol of the system controller 22. These three mirror elements can besynchronously moved in a number of different ways. For example, themirrors 37A′, 37B′ and 9′ can be jointly rotated together under thecontrol of one or more motor-driven mechanisms, or each mirror elementcan be driven by a separate driven motor which are synchronouslycontrolled to enable the composite planar laser illumination beam andFOV to move together in a spatially-coplanar manner during illuminationand detection operations within the PLIIM system.

[0405]FIG. 2I4 illustrates in greater detail the structure of the IFDmodule 3′ used in the PLIIM system of FIG. 2I1. As shown, the IFD module3′ comprises a variable focus fixed focal length imaging subsystem 3B′and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3A1 mounted along theoptical bench before the image detecting array 3A, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis in response to a first set of control signals 3Egenerated by the system controller 22, while the entire group of focallens elements 3B′ remain stationary. Alternatively, focal distancecontrol can also be provided by moving the entire group of focal lenselements 3B′ back and forth with a translator 3C in response to a firstset of control signals 3E generated by the system controller 22, whilethe 1-D image detecting array 3A remains stationary. In customizedapplications, it is possible for the individual lens elements in thegroup of focusing lens elements 3B′ to be moved in response to controlsignals generated by the system controller 22. Regardless of theapproach taken, an IFD module 3′ with variable focus fixed focal lengthimaging can be realized in a variety of ways, each being embraced by thespirit of the present invention.

[0406] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 3′, the folding/sweeping FOV mirror 9′, and the planar laserillumination beam folding/sweeping mirrors 37A′ and 37B′ employed inthis generalized system embodiment, are fixedly mounted on an opticalbench or chassis 8 so as to prevent any relative motion (which might becaused by vibration or temperature changes) between: (i) the imageforming optics (e.g. imaging lens) within the image formation anddetection module 3′ and the FOV folding/sweeping mirror 9′ employedtherewith; and (ii) each planar laser illumination module (i.e.VLD/cylindrical lens assembly) and the planar laser illumination beamfolding/sweeping mirrors 37A′ and 37B′ employed in this PLIIM systemconfiguration. Preferably, the chassis assembly should provide for easyand secure alignment of all optical components employed in the planarlaser illumination arrays 6A and 6B , beam folding/sweeping mirrors 37A′and 37B′, the image formation and detection module 3′ and FOVfolding/sweeping mirror 9′, as well as be easy to manufacture, serviceand repair. Also, this generalized PLIIM system embodiment 40′ employsthe general “planar laser illumination” and “focus beam at farthestobject distance (FBAFOD)” principles described above.

[0407] Applications for the Fourth Generalized Embodiment of the PLIIMSystem of the Present Invention

[0408] As the PLIIM systems shown in FIGS. 2I1 through 2I4 employ (i) anIFD module having a linear image detecting array and an imagingsubsystem having variable focus (i.e. focal distance) control, and (ii)a mechanism for automatically sweeping both the planar (2-D) FOV andplanar laser illumination beam through a 3-D scanning field in an “upand down” pattern while maintaining the inventive principle of“laser-beam/FOV coplanarity” hereindisclosed, such PLIIM systems aregood candidates for use in a hand-held scanner application, shown inFIGS. 2I5, and the hands-free presentation scanner applicationillustrated in FIG. 2I6. The provision of variable focal distancecontrol in these illustrative PLIIM systems is most sufficient for thehand-held scanner application shown in FIG. 2I5, and presentationscanner application shown in FIGS. 2I6, as the demands placed on thedepth of field and variable focus control characteristics of suchsystems will not be severe.

[0409] Fifth Generalized Embodiment of the PLIIM System of the PresentInvention

[0410] The fifth generalized embodiment of the PLIIM system of thepresent invention 50 is illustrated in FIG. 3A. As shown therein, thePLIIM system 50 comprises: a housing 2 of compact construction; a linear(i.e. 1-dimensional) type image formation and detection (IFD) module 3″including a 1-D electronic image detection array 3A, a linear (1-D)imaging subsystem (LIS) 3B″ having a variable focal length, a variablefocal distance, and a variable field of view (FOV), for forming a 1-Dimage of an illuminated object located within the fixed focal distanceand FOV thereof and projected onto the 1-D image detection array 3A, sothat the 1-D image detection array 3A can electronically detect theimage formed thereon and automatically produce a digital image data set5 representative of the detected image for subsequent image processing;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B, eachmounted on opposite sides of the IFD module 3″, such that each planarlaser illumination array 6A and 6B produces a plane of laser beamillumination 7A, 7B which is disposed substantially coplanar with thefield view of the image formation and detection module 3″ during objectillumination and image detection operations carried out by the PLIIMsystem.

[0411] In the PLIIM system of FIG. 3A, the linear image formation anddetection (IFD) module 3″ has an imaging lens with a variable focallength (i.e. a zoom-type imaging lens) 3B1, that has a variable angularfield of view (FOV); that is, the farther the target object is locatedfrom the IFD module, the larger the projection dimensions of the imagingsubsystem's FOV become on the surface of the target object. A zoomimaging lens is capable of changing its focal length, and therefore itsangular field of view (FOV) by moving one or more of its component lenselements. The position at which the zooming lens element(s) must be inorder to achieve a given focal length is determined by consulting alookup table, which must be constructed ahead of time eitherexperimentally or by design software, in a manner well known in the art.An advantage to using a zoom lens is that the resolution of the imagethat is acquired, in terms of pixels or dots per inch, remains constantno matter what the distance from the target object to the lens. However,a zoom camera lens is more difficult and more expensive to design andproduce than the alternative, a fixed focal length camera lens.

[0412] The image formation and detection (IFD) module 3″ in the PLIIMsystem of FIG. 3A also has an imaging lens 3B2 with variable focaldistance, which can adjust its image distance to compensate for a changein the target's object distance. Thus, at least some of the componentlens elements in the imaging subsystem 3B2 are movable, and the depth offield (DOF) of the imaging subsystem does not limit the ability of theimaging subsystem to accommodate possible object distances andorientations. This variable focus imaging subsystem 3B2 is able to moveits components in such a way as to change the image distance of theimaging lens to compensate for a change in the target's object distance,thus preserving good image focus no matter where the target object mightbe located. This variable focus technique can be practiced in severaldifferent ways, namely: by moving lens elements in the imagingsubsystem; by moving the image detection/sensing array relative to theimaging lens; and by dynamic focus control. Each of these differentmethods has been described in detail above.

[0413] In accordance with the present invention, the planar laserillumination arrays 6A and 6B the image formation and detection module3″ are fixedly mounted on an optical bench or chassis assembly 8 so asto prevent any relative motion between (i) the image forming optics(e.g. camera lens) within the image formation and detection module 3″and (ii) each planar laser illumination module (i.e. VLD/cylindricallens assembly) employed in the PLIIM system which might be caused byvibration or temperature changes. Preferably, the chassis assemblyshould provide for easy and secure alignment of all optical componentsemployed in the planar laser illumination arrays 6A and 6B as well asthe image formation and detection module 3″, as well as be easy tomanufacture, service and repair. Also, this PLIIM system employs thegeneral “planar laser illumination” and “FBAFOD” principles describedabove.

[0414] First Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 3B1

[0415] The first illustrative embodiment of the PLIIM system of FIG. 3A50A is shown in FIG. 3B1. As illustrated therein, the field of view ofthe image formation and detection module 3″ and the first and secondplanar laser illumination beams 7A and 7B produced by the planarillumination arrays 6A and 6B, respectively, are arranged in asubstantially coplanar relationship during object illumination and imagedetection operations.

[0416] The PLIIM system 50A illustrated in FIG. 3B1 is shown in greaterdetail in FIG. 3B2. As shown therein, the linear image formation anddetection module 3″ is shown comprising an imaging subsystem 3B″, and alinear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B″. The imagingsubsystem 3B″ has a variable focal length imaging lens, a variable focaldistance and a variable field of view. As shown, each planar laserillumination array 6A, 6B comprises a plurality of planar laserillumination modules (PLIMs) 11A through 11F, closely arranged relativeto each other, in a rectilinear fashion. As taught hereinabove, therelative spacing of each PLIM 11 is such that the spatial intensitydistribution of the individual planar laser beams superimpose andadditively provide a composite planar case illumination beam havingsubstantially uniform composite spatial intensity distribution for theentire planar laser illumination array 6A and 6B.

[0417] As shown in FIG. 3C1, the PLIIM system 50A of FIG. 3B1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3″; an image frame grabber 19operably connected to the linear-type image formation and detectionmodule 3A, for accessing 1-D images (i.e. 1-D digital image data sets)therefrom and building a 2-D digital image of the object beingilluminated by the planar laser illumination arrays 6A and 6B; an imagedata buffer (e.g. VRAM) 20 for buffering 2-D images received from theimage frame grabber 19; a decode image processor 21, operably connectedto the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.

[0418]FIG. 3C2 illustrates in greater detail the structure of the IFDmodule 3″ used in the PLIIM system of FIG. 3B1. As shown, the IFD module3″ comprises a variable focus variable focal length imaging subsystem3B″ and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B′ comprises: a first group of focal lens elements3A1 mounted stationary relative to the image detecting array 3A; asecond group of lens elements 3B2, functioning as a focal lens assembly,movably mounted along the optical bench in front of the first group ofstationary lens elements 3A1; and a third group of lens elements 3B1,functioning as a zoom lens assembly, movably mounted between the secondgroup of focal lens elements and the first group of stationary focallens elements 3A1. In a non-customized application, focal distancecontrol can also be provided by moving the second group of focal lenselements 3B2 back and forth with translator 3C1 in response to a firstset of control signals generated by the system controller 22, while the1-D image detecting array 3A remains stationary. Alternatively, focaldistance control can be provided by moving the 1-D image detecting array3A back and forth along the optical axis with translator 3C1 in responseto a first set of control signals 3E2 generated by the system controller22, while the second group of focal lens elements 3B2 remain stationary.For zoom control (i.e. variable focal length control), the focal lenselements in the third group 3B2 are typically moved relative to eachother with translator 3C1 in response to a second set of control signals3E2 generated by the system controller 22. Regardless of the approachtaken in any particular illustrative embodiment, an IFD module withvariable focus variable focal length imaging can be realized in avariety of ways, each being embraced by the spirit of the presentinvention.

[0419] A preferred implementation of the image subsystem of FIG. 3C2 isshown in FIG. 3D. As shown in FIG. 3D, imaging subsystem 3B″ comprises:an optical bench 3D having a pair of rails, along which mounted opticalelements are translated; a linear CCD-type image detection array 3A(e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line ScanCamera, from Dalsa, Inc. USA—http:/www/dalsa.com) fixedly mounted to oneend of the optical bench; a system of stationary lenses 3A1 fixedlymounted before the CCD-type linear image detection array 3A; a firstsystem of movable lenses 3B1 slidably mounted to the rails of theoptical bench 3D by a set of ball bearings, and designed for steppedmovement relative to the stationary lens subsystem 3A1 with translator3C1 in automatic response to a first set of control signals 3E1generated by the system controller 22; and a second system of movablelenses 3B2 slidably mounted to the rails of the optical bench by way ofa second set of ball bearings, and designed for stepped movementsrelative to the first system of movable lenses 3B with translator 3C2 inautomatic response to a second set of control signals 3D2 generated bythe system controller 22. As shown in FIG. 3D, a large stepper wheel 42driven by a zoom stepper motor 43 engages a portion of the zoom lenssystem 3B1 to move the same along the optical axis of the stationarylens system 3A1 in response to control signals 3C1 generated from thesystem controller 22. Similarly, a small stepper wheel 44 driven by afocus stepper motor 45 engages a portion of the focus lens system 3B2 tomove the same along the optical axis of the stationary lens system 3A1in response to control signals 3E2 generated from the system controller22.

[0420] Method of Adjusting the Focal Characteristics of the Planar LaserIllumination Beams Generated by Planar Laser Illumination Arrays Used inConjunction with Image Formation and Detection Modules EmployingVariable Focal Length (Zoom) Imaging Lenses

[0421] Unlike the fixed focal length imaging lens case, there occurs asignificant a 1/r² drop-off in laser return light intensity at the imagedetection array when using a zoom (variable focal length) imaging lensin the PLIIM system hereof. In PLIIM system employing an imagingsubsystem having a variable focal length imaging lens, the area of theimaging subsystem's field of view (FOV) remains constant as the workingdistance increases. Such variable focal length control is used to ensurethat each image formed and detected by the image formation and detection(IFD) module 3″ has the same number of “dots per inch” (DPI) resolution,regardless of the distance of the target object from the IFD module 3″.However, since module's field of view does not increase in size with theobject distance, equation (8) must be rewritten as the equation (10) setforth below $\begin{matrix}{E_{ccd}^{zoom} = \frac{E_{0}f^{2}s^{2}}{8d^{2}F^{2}r^{2}}} & (10)\end{matrix}$

[0422] where s² is the area of the field of view and d² is the area of apixel on the image detecting array. This expression is a strong functionof the object distance, and demonstrates 1/r² drop off of the returnlight. If a zoom lens is to be used, then it is desirable to have agreater power density at the farthest object distance than at thenearest, to compensate for this loss. Again, focusing the beam at thefarthest object distance is the technique that will produce this result.

[0423] Therefore, in summary, where a variable focal length (i.e. zoom)imaging subsystem is employed in the PLIIM system, the planar laser beamfocusing technique of the present invention described above helpscompensate for (i) decreases in the power density of the incidentillumination beam due to the fact that the width of the planar laserillumination beam increases for increasing distances away from theimaging subsystem, and (ii) any 1/r² type losses that would typicallyoccur when using the planar laser planar illumination beam of thepresent invention.

[0424] Second Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 3A

[0425] The second illustrative embodiment of the PLIIM system of FIG. 3A50B is shown in FIG. 3E1 comprising: an image formation and detectionmodule 3″ having an imaging subsystem 3B with a variable focal lengthimaging lens, a variable focal distance and a variable field of view,and a linear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B″; a field of viewfolding mirror 9 for folding the field of view of the image formationand detection module 3″; and a pair of planar laser illumination arrays6A and 6B arranged in relation to the image formation and detectionmodule 3″ such that the field of view thereof folded by the field ofview folding mirror 9 is oriented in a direction that is coplanar withthe composite plane of laser illumination 12 produced by the planarillumination arrays, during object illumination and image detectionoperations, without using any laser beam folding mirrors.

[0426] As shown in FIG. 3E2, the PLIIM system of FIG. 3E1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3A; a field of view folding mirror9′ for folding the field of view of the image formation and detectionmodule 3″; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3″, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

[0427]FIG. 3E3 illustrates in greater detail the structure of the IFDmodule 3″ used in the PLIIM system of FIG. 3E1. As shown, the IFD module3″ comprises a variable focus variable focal length imaging subsystem3B″ and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B″ comprises: a first group of focal lens elements3A1 mounted stationary relative to the image detecting array 3A; asecond group of lens elements 3B2, functioning as a focal lens assembly,movably mounted along the optical bench in front of the first group ofstationary lens elements 3A; and a third group of lens elements 3B1,functioning as a zoom lens assembly, movably mounted between the secondgroup of focal lens elements and the first group of stationary focallens elements 3B2. In a non-customized application, focal distancecontrol can also be provided by moving the second group of focal lenselements 3B2 back and forth with translator 3C2 in response to a firstset of control signals 3E2 generated by the system controller 22, whilethe 1-D image detecting array 3A remains stationary. Alternatively,focal distance control can be provided by moving the 1-D image detectingarray 3A back and forth along the optical axis with translator 3C2 inresponse to a first set of control signals 3E2 generated by the systemcontroller 22, while the second group of focal lens elements 3B2 remainstationary. For zoom control (i.e. variable focal length control), thefocal lens elements in the third group 3B1 are typically moved relativeto each other with translator 3C1 in response to a second set of controlsignals 3E1 generated by the system controller 22. Regardless of theapproach taken in any particular illustrative embodiment, an IFD module3″ with variable focus variable focal length imaging can be realized ina variety of ways, each being embraced by the spirit of the presentinvention.

[0428] Detailed Description of an Exemplary Realization of the PLIIMSystem Shown in FIG. 3E1 Through 3E3

[0429] Referring now to FIGS. 3E4 through 3E8, an exemplary realizationof the PLIIM system 50B shown in FIGS. 3E1 through 3E3 will now bedescribed in detail below.

[0430] As shown in FIGS. 3E41 and 3E5, an exemplary realization of thePLIIM system 50B FIGS. 3E1-3E3 is indicated by reference numeral 25′contained within a compact housing 2 having height, length and widthdimensions of about 4.5″, 21.7″ and 19.7″, respectively, to enable easymounting above a conveyor belt structure or the like. As shown in FIG.3E4, 3E5 and 3E6, the PLIIM system comprises a linear image formationand detection module 3″, a pair of planar laser illumination arrays 6A,and 6B, and a field of view (FOV) folding structure (e.g. mirror,refractive element, or diffractive element) 9. The function of the FOVfolding mirror 9 is to fold the field of view (FOV) 10 of the imageformation and detection module 3′ in an imaging direction that iscoplanar with the plane of laser illumination beams 7A and 7B producedby the planar illumination arrays 6A and 6B. As shown, these componentsare fixedly mounted to an optical bench 8 supported within the compacthousing 2 so that these optical components are forced to oscillatetogether. The linear CCD imaging array 3A can be realized using avariety of commercially available high-speed line-scan camera systemssuch as, for example, the Piranha Model Nos. CT-P4, or CL-P4 High-SpeedCCD Line Scan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com. Notably,image frame grabber 19, image data buffer (e.g. VRAM) 20, decode imageprocessor 21, and system controller 22 are realized on one or moreprinted circuit (PC) boards contained within a camera and systemelectronic module 27 also mounted on the optical bench, or elsewhere inthe system housing 2.

[0431] While this system design requires additional optical surfaces(i.e. planar laser beam folding mirrors) which complicateslaser-beam/FOV alignment, and attenuates slightly the intensity ofcollected laser return light, this system design will be beneficial whenthe FOV of the imaging subsystem cannot have a large apex angle, asdefined as the angular aperture of the imaging lens (in the zoom lensassembly), due to the fact that the IFD module 3″ must be mounted on theoptical bench in a backed-off manner to the conveyor belt (or maximumobject distance plane), and a longer focal length lens (or zoom lenswith a range of longer focal lengths) is chosen.

[0432] One notable advantage of this system design is that it enables aconstruction having an ultra-low height profile suitable, for example,in unitary package identification and dimensioning systems of the typedisclosed in FIGS. 17-22, wherein the image-based bar code symbol readerneeds to be installed within a compartment (or cavity) of a housinghaving relatively low height dimensions. Also, in this system design,there is a relatively high degree of freedom provided in where the imageformation and detection module 3″ can be mounted on the optical bench ofthe system, thus enabling the field of view (FOV) folding techniquedisclosed in FIG. 1L1 to be practiced in a relatively easy manner.

[0433] As shown in FIG. 3E4, the compact housing 2 has a relatively longlight transmission window 28 of elongated dimensions for the projectingthe FOV 10 of the image formation and detection module 3″ through thehousing towards a predefined region of space outside thereof, withinwhich objects can be illuminated and imaged by the system components onthe optical bench. Also, the compact housing 2 has a pair of relativelyshort light transmission apertures 30A and 30B, closely disposed onopposite ends of light transmission window 28, with minimal spacingtherebetween, as shown in FIG. 3E4. Such spacing is to ensure that theFOV emerging from the housing 2 can spatially overlap in a coplanarmanner with the substantially planar laser illumination beams projectedthrough transmission windows 29A and 29B, as close to transmissionwindow 28 as desired by the system designer, as shown in FIGS. 3E6 and3E7. Notably, in some applications, it is desired for such coplanaroverlap between the FOV and planar laser illumination beams to occurvery close to the light transmission windows 28, 29A and 29B (i.e. atshort optical throw distances), but in other applications, for suchcoplanar overlap to occur at large optical throw distances.

[0434] In either event, each planar laser illumination array 6A and 6Bis optically isolated from the FOV of the image formation and detectionmodule 3″ to increase the signal-to-noise ratio (SNR) of the system. Inthe preferred embodiment, such optical isolation is achieved byproviding a set of opaque wall structures 30A, 30B about each planarlaser illumination array, extending from the optical bench 8 to itslight transmission window 29A or 29B, respectively. Such opticalisolation structures prevent the image formation and detection module 3″from detecting any laser light transmitted directly from the planarlaser illumination arrays 6A and 6B within the interior of the housing.Instead, the image formation and detection module 3″ can only receiveplanar laser illumination that has been reflected off an illuminatedobject, and focused through the imaging subsystem 3B″ of the IFD module3″.

[0435] Notably, the linear image formation and detection module of thePLIIM system of FIG. 3E4 has an imaging subsystem 3B″ with a variablefocal length imaging lens, a variable focal distance, and a variablefield of view. In FIG. 3E8, the spatial limits for the FOV of the imageformation and detection module are shown for two different scanningconditions, namely: when imaging the tallest package moving on aconveyor belt structure; and when imaging objects having height valuesclose to the surface of the conveyor belt structure. In a PLIIM systemhaving a variable focal length imaging lens and a variable focusingmechanism, the PLIIM system would be capable of imaging at either of thetwo conditions indicated above.

[0436] Third Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 3A

[0437] The third illustrative embodiment of the PLIIM system of FIG. 3A50C is shown in FIG. 3F1 comprising: an image formation and detectionmodule 3″ having an imaging subsystem 3B″ with a variable focal lengthimaging lens, a variable focal distance and a variable field of view,and a linear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B″; a pair ofplanar laser illumination arrays 6A and 6B for producing first andsecond planar laser illumination beams 7A and 7B, respectively; and apair of planar laser beam folding mirrors 37A and 37B for folding theplanes of the planar laser illumination beams produced by the pair ofplanar illumination arrays 6A and 6B, in a direction that is coplanarwith the plane of the FOV of the image formation and detection module 3″during object illumination and imaging operations.

[0438] One notable disadvantage of this system architecture is that itrequires additional optical surfaces (i.e. the planar laser beam foldingmirrors) which reduce outgoing laser light and therefore the returnlaser light slightly. Also this system design requires a morecomplicated beam/FOV adjustment scheme than the direct-viewing designshown in FIG. 3B1. Thus, this system design can be best used when theplanar laser illumination beams do not have large apex angles to providesufficiently uniform illumination. Notably, in this system embodiment,the PLIMs are mounted on the optical bench as far back as possible fromthe beam folding mirrors 37A and 37B, and cylindrical lenses 16 withlarger radiuses will be employed in the design of each PLIM 11A through11P.

[0439] As shown in FIG. 3F2, the PLIIM system of FIG. 3F1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3A;; a pair of planar laserillumination beam folding mirrors 37A and 37B, for folding the planarlaser illumination beams 7A and 7B in the imaging direction; an imageframe grabber 19 operably connected to the linear-type image formationand detection module 3″, for accessing 1-D images (i.e. 1-D digitalimage data sets) therefrom and building a 2-D digital image of theobject being illuminated by the planar laser illumination arrays 6A and6B; an image data buffer (e.g. VRAM) 20 for buffering 2-D imagesreceived from the image frame grabber 19; a decode image processor 21,operably connected to the image data buffer 20, for carrying out imageprocessing algorithms (including bar code symbol decoding algorithms)and operators on digital images stored within the image data buffer; anda system controller 22 operably connected to the various componentswithin the system for controlling the operation thereof in anorchestrated manner.

[0440]FIG. 3F3 illustrates in greater detail the structure of the IFDmodule 3″ used in the PLIIM system of FIG. 3F1. As shown, the IFD module3″ comprises a variable focus variable focal length imaging subsystem3B″ and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B′ comprises: a first group of focal lens elements3A′ mounted stationary relative to the image detecting array 3A; asecond group of lens elements 3B2 , functioning as a focal lensassembly, movably mounted along the optical bench 3D in front of thefirst group of stationary lens elements 3A1; and a third group of lenselements 3B1, functioning as a zoom lens assembly, movably mountedbetween the second group of focal lens elements and the first group ofstationary focal lens elements 3A1. In a non-customized application,focal distance control can also be provided by moving the second groupof focal lens elements 3B2 back and forth in response to a first set ofcontrol signals generated by the system controller, while the 1-D imagedetecting array 3A remains stationary. Alternatively, focal distancecontrol can be provided by moving the 1-D image detecting array 3A backand forth along the optical axis with translator in response to a firstset of control signals 3E2 generated by the system controller 22, whilethe second group of focal lens elements 3B2 remain stationary. For zoomcontrol (i.e. variable focal length control), the focal lens elements inthe third group 3B1 are typically moved relative to each other withtranslator 3C1 in response to a second set of control signals 3E1generated by the system controller 22. Regardless of the approach takenin any particular illustrative embodiment, an IFD module with variablefocus variable focal length imaging can be realized in a variety ofways, each being embraced by the spirit of the present invention.

[0441] Fourth Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 3A

[0442] The fourth illustrative embodiment of the PLIIM system of FIG. 3A50D is shown in FIG. 3G1 comprising: an image formation and detectionmodule 3″ having an imaging subsystem 3B″ with a variable focal lengthimaging lens, a variable focal distance and a variable field of view,and a linear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B″; a FOV foldingmirror 9 for folding the FOV of the imaging subsystem in the directionof imaging; a pair of planar laser illumination arrays 6A and 6B forproducing first and second planar laser illumination beams 7A, 7B; and apair of planar laser beam folding mirrors 37A and 37B for folding theplanes of the planar laser illumination beams produced by the pair ofplanar illumination arrays 6A and 6B, in a direction that is coplanarwith the plane of the FOV of the image formation and detection moduleduring object illumination and image detection operations.

[0443] As shown in FIG. 3G2, the PLIIM system of FIG. 3G1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3″; a FOV folding mirror 9 forfolding the FOV of the imaging subsystem in the direction of imaging; apair of planar laser illumination beam folding mirrors 37A and 37B, forfolding the planar laser illumination beams 7A and 7B in the imagingdirection; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3″, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer 20; and a system controller 22 operably connected tothe various components within the system for controlling the operationthereof in an orchestrated manner.

[0444]FIG. 3G3 illustrates in greater detail the structure of the IFDmodule 3″ used in the PLIIM system of FIG. 3G1. As shown, the IFD module3″ comprises a variable focus variable focal length imaging subsystem3B″ and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B′ comprises: a first group of focal lens elements3A1 mounted stationary relative to the image detecting array 3A; asecond group of lens elements 3B2, functioning as a focal lens assembly,movably mounted along the optical bench in front of the first group ofstationary lens elements 3A1; and a third group of lens elements 3B1,functioning as a zoom lens assembly, movably mounted between the secondgroup of focal lens elements and the first group of stationary focallens elements 3A1. In a non-customized application, focal distancecontrol can also be provided by moving the second group of focal lenselements 3B2 back and forth with translator 3C2 in response to a firstset of control signals 3E2 generated by the system controller 22, whilethe 1-D image detecting array 3A remains stationary. Alternatively,focal distance control can be provided by moving the 1-D image detectingarray 3A back and forth along the optical axis in response to a firstset of control signals 3E2 generated by the system controller 22, whilethe second group of focal lens elements 3B2 remain stationary. For zoomcontrol (i.e. variable focal length control), the focal lens elements inthe third group 3B1 are typically moved relative to each other withtranslator 3C1 in response to a second set of control signals 3C1generated by the system controller 22. Regardless of the approach takenin any particular illustrative embodiment, an IFD module with variablefocus variable focal length imaging can be realized in a variety ofways, each being embraced by the spirit of the present invention.

[0445] Applications for the Fifth Generalized Embodiment of the PLIIMSystem of the Present Invention, and the Illustrative EmbodimentsThereof

[0446] As the PLIIM systems shown in FIGS. 3A through 3G3 employ an IFDmodule having a linear image detecting array and an imaging subsystemhaving variable focal length (zoom) and variable focus (i.e. focaldistance) control mechanisms, such PLIIM systems are good candidates foruse in the conveyor top scanner application shown in FIG. 3H, asvariations in target object distance can be up to a meter or more (fromthe imaging subsystem) and the imaging subsystem provided therein caneasily accommodate such object distance parameter variations duringobject illumination and imaging operations. Also, by adding dynamicfocusing functionality to the imaging subsystem of any of theembodiments shown in FIGS. 3A through 3F3, the resulting PLIIM systemwill become appropriate for the conveyor side scanning application alsoshown in FIG. 3G, where the demands on the depth of field and variablefocus or dynamic focus requirements are greater compared to a conveyortop scanner application.

[0447] Sixth Generalized Embodiment of the Planar Laser Illumination andElectronic Imaging System of the Present Invention

[0448] The sixth generalized embodiment of the PLIIM system of FIG. 3A50′ is illustrated in FIGS. 3J1 and 3J2. As shown in FIG. 3J1, the PLIIMsystem 50′ comprises: a housing 2 of compact construction; a linear(i.e. 1-dimensional) type image formation and detection (IFD) module 3″;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B mountedon opposite sides of the IFD module 3″. During system operation, laserillumination arrays 6A and 6B each produce a composite laserillumination beam 12 which synchronously moves and is disposedsubstantially coplanar with the field of view (FOV) of the imageformation and detection module 3″, so as to scan a bar code symbol orother graphical structure 4 disposed stationary within a 2-D scanningregion.

[0449] As shown in FIGS. 3J2 and 3J3, the PLIIM system of FIG. 3J1 50′comprises: an image formation and detection module 3″ having an imagingsubsystem 3B″ with a variable focal length imaging lens, a variablefocal distance and a variable field of view, and a linear array ofphoto-electronic detectors 3A realized using CCD technology (e.g.Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D line imagesformed thereon by the imaging subsystem 3B″; a field of view folding andsweeping mirror 9′ for folding and sweeping the field of view of theimage formation and detection module 3″; a pair of planar laserillumination arrays 6A and 6B for producing planar laser illuminationbeams 7A and 7B; a pair of planar laser illumination beam folding andsweeping mirrors 37A′ and 37B′ for folding and sweeping the planar laserillumination beams 7A and 7B, respectively, in synchronism with the FOVbeing swept by the FOV folding and sweeping mirror 9′; an image framegrabber 19 operably connected to the linear-type image formation anddetection module 3A, for accessing 1-D images (i.e. 1-D digital imagedata sets) therefrom and building a 2-D digital image of the objectbeing illuminated by the planar laser illumination arrays 6A and 6B; animage data buffer (e.g. VRAM) 20 for buffering 2-D images received fromthe image frame grabber 19; a decode image processor 21, operablyconnected to the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.

[0450] As shown in FIG. 3J3, each planar laser illumination module 11Athrough 11F is driven by a VLD driver circuit 18 under the systemcontroller 22 in a manner well known in the art. Notably, laserillumination beam folding/sweeping mirror 37A′ and 37B′, and FOVfolding/sweeping mirror 9′ are each rotatably driven by a motor-drivenmechanism 39A, 39B, and 38, respectively, operated under the control ofthe system controller 22. These three mirror elements can besynchronously moved in a number of different ways. For example, themirrors 37A′, 37B′ and 9′ can be jointly rotated together under thecontrol of one or more motor-driven mechanisms, or each mirror elementcan be driven by a separate driven motor which are synchronouslycontrolled to enable the planar laser illumination beams and FOV to movetogether during illumination and detection operations within the PLIIMsystem.

[0451]FIG. 3J4 illustrates in greater detail the structure of the IFDmodule 3″ used in the PLIIM system of FIG. 3J1. As shown, the IFD module3″ comprises a variable focus variable focal length imaging subsystem3B′ and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B″ comprises: a first group of focal lens elements3B″ mounted stationary relative to the image detecting array 3A1 asecond group of lens elements 3B2, functioning as a focal lens assembly,movably mounted along the optical bench in front of the first group ofstationary lens elements 3A1; and a third group of lens elements 3B1,functioning as a zoom lens assembly, movably mounted between the secondgroup of focal lens elements and the first group of stationary focallens elements 3A1. In a non-customized application, focal distancecontrol can also be provided by moving the second group of focal lenselements 3B2 back and forth in response to a first set of controlsignals generated by the system controller, while the 1-D imagedetecting array 3A remains stationary. Alternatively, focal distancecontrol can be provided by moving the 1-D image detecting array 3A backand forth along the optical axis with translator 3C2 in response to afirst set of control signals 3E1 generated by the system controller 22,while the second group of focal lens elements 3B2 remain stationary. Forzoom control (i.e. variable focal length control), the focal lenselements in the third group 3B1 are typically moved relative to eachother with translator 3C1 in response to a second set of control signals3E1 generated by the system controller 22. Regardless of the approachtaken in any particular illustrative embodiment, an IFD module withvariable focus variable focal length imaging can be realized in avariety of ways, each being embraced by the spirit of the presentinvention.

[0452] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 3″, the folding/sweeping FOV mirror 9′, and the planar laserillumination beam folding/sweeping mirrors 37A′ and 37B′ employed inthis generalized system embodiment, are fixedly mounted on an opticalbench or chassis 8 so as to prevent any relative motion (which might becaused by vibration or temperature changes) between: (i) the imageforming optics (e.g. imaging lens) within the image formation anddetection module 3″ and the FOV folding/sweeping mirror 9′ employedtherewith; and (ii) each planar laser illumination module (i.e.VLD/cylindrical lens assembly) and the planar laser illumination beamfolding/sweeping mirrors 37A′ and 37B′ employed in this PLIIM systemconfiguration. Preferably, the chassis assembly should provide for easyand secure alignment of all optical components employed in the planarlaser illumination arrays 6A and 6B, beam folding/sweeping mirrors 37A′and 37B′, the image formation and detection module 3″ and FOVfolding/sweeping mirror 9′, as well as be easy to manufacture, serviceand repair. Also, this generalized PLIIM system embodiment employs thegeneral “planar laser illumination” and “focus beam at farthest objectdistance (FBAFOD)” principles described above.

[0453] Applications for the Sixth Generalized Embodiment of the PLIIMSystem of the Present Invention

[0454] As the PLIIM systems shown in FIGS. 3J1 through 3J4 employ (i) anIFD module having a linear image detecting array and an imagingsubsystem having variable focal length (zoom) and variable focaldistance control mechanisms, and also (ii) a mechanism for automaticallysweeping both the planar (2-D) FOV and planar laser illumination beamthrough a 3-D scanning field in a raster-like pattern while maintainingthe inventive principle of “laser-beam/FOV coplanarity” hereindisclosed, such PLIIM systems are good candidates for use in a hand-heldscanner application, shown in FIG. 3J5, and the hands-free presentationscanner application illustrated in FIG. 3J6. As such, these embodimentsof the present invention are ideally suited for use in hand-supportableand presentation-type hold-under bar code symbol reading applicationsshown in FIGS. 3J5 and 3J6, respectively, in which raster—like (“up anddown”) scanning patterns can be used for reading 1-D as well as 2-D barcode symbologies such as the PDF 147 symbology. In general, the PLIMsystem of this generalized embodiment may have any of the housing formfactors disclosed and described in Applicant's copending U.S.application Ser. No. 09/204,17+ filed Dec. 3, 1998, U.S. applicationSer. No. 09/452,976 filed Dec. 2, 1999, and WIPO Publication No. WO00/33239 published Jun. 8, 2000 incorporated herein by reference. Thebeam sweeping technology disclosed in copending application Ser. No.08/931,691 filed Sep. 16, 1997, incorporated herein by reference, can beused to uniformly sweep both the planar laser illumination beam andlinear FOV in a coplanar manner during illumination and imagingoperations.

[0455] Seventh Generalized Embodiment of the PLIIM System of the PresentInvention

[0456] The seventh generalized embodiment of the PLIIM system of thepresent invention 60 is illustrated in FIG. 4A. As shown therein, thePLIIM system 60 comprises: a housing 2 of compact construction; an area(i.e. 2-dimensional) type image formation and detection (IFD) module 55including a 2-D electronic image detection array 55A, and an area (2-D)imaging subsystem (LIS) 55B having a fixed focal length, a fixed focaldistance, and a fixed field of view (FOV), for forming a 2-D image of anilluminated object located within the fixed focal distance and FOVthereof and projected onto the 2-D image detection array 55A, so thatthe 2-D image detection array 55A can electronically detect the imageformed thereon and automatically produce a digital image data set 5representative of the detected image for subsequent image processing;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B, eachmounted on opposite sides of the IFD module 55, for producing first andsecond planes of laser beam illumination 7A and 7B that are folded andswept so that the planar laser illumination beams are disposedsubstantially coplanar with a section of the FOV of image formation anddetection module 55 during object illumination and image detectionoperations carried out by the PLIIM system.

[0457] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 55, and any stationary FOV folding mirror employed in anyconfiguration of this generalized system embodiment, are fixedly mountedon an optical bench or chassis so as to prevent any relative motion(which might be caused by vibration or temperature changes) between: (i)the image forming optics (e.g. imaging lens) within the image formationand detection module 55 and any stationary FOV folding mirror employedtherewith; and (ii) each planar laser illumination module (i.e.VLD/cylindrical lens assembly) and each planar laser illumination beamfolding/sweeping mirror employed in the PLIIM system configuration.Preferably, the chassis assembly should provide for easy and securealignment of all optical components employed in the planar laserillumination arrays 6A and 6B as well as the image formation anddetection module 55, as well as be easy to manufacture, service andrepair. Also, this generalized PLIIM system embodiment employs thegeneral “planar laser illumination” and “focus beam at farthest objectdistance (FBAFOD)” principles described above. Various illustrativeembodiments of this generalized PLIIM system will be described below.

[0458] First Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 4A

[0459] The first illustrative embodiment of the PLIIM system of FIG. 4A60A is shown in FIG. 4B1 comprising: an image formation and detectionmodule (i.e. camera) 55 having an imaging subsystem 55B with a fixedfocal length imaging lens, a fixed focal distance and a fixed field ofview (FOV) of three-dimensional extent, and an area (2-D) array ofphoto-electronic detectors 55A realized using high-speed CCD technology(e.g. the Sony ICX085AL Progressive Scan CCD Image Sensor with SquarePixels for B/W Cameras, or the Kodak KAF-4202 Series 2032(H)×2044(V)Full-Frame CCD Image Sensor) for detecting 2-D area images formedthereon by the imaging subsystem 55B; a pair of planar laserillumination arrays 6A and 6B for producing first and second planarlaser illumination beams 7A and 7B; and a pair of planar laserillumination beam folding/sweeping mirrors 57A and 57B, arranged inrelation to the planar laser illumination arrays 6A and 6B,respectively, such that the planar laser illumination beams 7A, 7B arefolded and swept so that the planar laser illumination beams aredisposed substantially coplanar with a section of the 3-D FOV 40′ ofimage formation and detection module during object illumination andimage detection operations carried out by the PLIIM system.

[0460] As shown in FIG. 4B2, the PLIIM system 60A of FIG. 4B1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; area-typeimage formation and detection module 55; planar laser illumination beamfolding/sweeping mirrors 57A and 57B; an image frame grabber 19 operablyconnected to area-type image formation and detection module 55, foraccessing 2-D digital images of the object being illuminated by theplanar laser illumination arrays 6A and 6B during image formation anddetection operations; an image data buffer (e.g. VRAM) 20 for buffering2-D images received from the image frame grabber 19; a decode imageprocessor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

[0461] Second Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 4A

[0462] The second illustrative embodiment of the PLIIM system of FIG. 4A601 is shown in FIG. 4C1 comprising: an image formation and detectionmodule 55 having an imaging subsystem 55B with a fixed focal lengthimaging lens, a fixed focal distance and a fixed field of view, and anarea (2-D) array of photo-electronic detectors 55A realized using CCDtechnology (e.g. the Sony ICX085AL Progressive Scan CCD Image Sensorwith Square Pixels for B/W Cameras, or the Kodak KAF-4202 Series2032(H)×2044(V) Full-Frame CCD Image Sensor) for detecting 2-D lineimages formed thereon by the imaging subsystem 55; a FOV folding mirror9 for folding the FOV in the imaging direction of the system; a pair ofplanar laser illumination arrays 6A and 6B for producing first andsecond planar laser illumination beams 7A and 7B; and a pair of planarlaser illumination beam folding/sweeping mirrors 57A and 57B, arrangedin relation to the planar laser illumination arrays 6A and 6B,respectively, such that the planar laser illumination beams 7A, 7B arefolded and swept so that the planar laser illumination beams aredisposed substantially coplanar with a section of the FOV of the imageformation and detection module during object illumination and imagedetection operations carried out by the PLIIM system.

[0463] In general, the area image detection array 55B employed in thePLIIM systems shown in FIGS. 4A through 6F4 has multiple rows andcolumns of pixels arranged in a rectangular array. Therefore, area imagedetection array is capable of sensing/detecting a complete 2-D image ofa target object in a single exposure, and the target object may bestationary with respect to the PLIIM system. Thus, the image detectionarray 55D is ideally suited for use in hold-under type scanning systemsHowever, the fact that the entire image is captured in a single exposureimplies that the technique of dynamic focus cannot be used with an areaimage detector.

[0464] As shown in FIG. 4C2, the PLIIM system of FIG. 4C1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11B, and each planar laserillumination module being driven by a VLD driver circuit 18; area-typeimage formation and detection module 55B; FOV folding mirror 9; planarlaser illumination beam folding/sweeping mirrors 57A and 57B; an imageframe grabber 19 operably connected to area-type image formation anddetection module 55, for accessing 2-D digital images of the objectbeing illuminated by the planar laser illumination arrays 6A and 6Bduring image formation and detection operations; an image data buffer(e.g. VRAM) 20 for buffering 2-D images received from the image framegrabber 19; a decode image processor 21, operably connected to the imagedata buffer 20, for carrying out image processing algorithms (includingbar code symbol decoding algorithms) and operators on digital imagesstored within the image data buffer; and a system controller 22 operablyconnected to the various components within the system for controllingthe operation thereof, including synchronous driving motors 58A and 68B,in an orchestrated manner.

[0465] Applications for the Seventh Generalized Embodiment of the PLIIMSystem of the Present Invention, and the Illustrative EmbodimentsThereof

[0466] The fixed focal distance area-type PLIIM systems shown in FIGS.4A through 4C2 are ideal for applications in which there is littlevariation in the object distance, such as in a 2-D hold-under scannerapplication as shown in FIG. 4D. A fixed focal distance PLIIM systemgenerally takes up less space than a variable or dynamic focus modelbecause more advanced focusing methods require more complicated opticsand electronics, and additional components such as motors. For thisreason, fixed focus PLIIM systems are good choices for the hands-freepresentation and hand-held scanners applications illustrated in FIGS. 4Dand 4E, respectively, wherein space and weight are always criticalcharacteristics. In these applications, however, the object distance canvary over a range from several to twelve or more inches, and so thedesigner must exercise care to ensure that the scanner's depth of field(DOF) alone will be sufficient to accommodate all possible variations intarget object distance and orientation. Also, because a fixed focusimaging subsystem implies a fixed focal length imaging lens, thevariation in object distance implies that the dpi resolution of acquiredimages will vary as well, and therefore image-based bar code symboldecode-processing techniques must address such variations in imageresolution. The focal length of the imaging lens must be chosen so thatthe angular width of the field of view (FOV) is narrow enough that thedpi image resolution will not fall below the minimum acceptable valueanywhere within the range of object distances supported by the PLIIMsystem.

[0467] Eighth Generalized Embodiment of the PLIIM System of the PresentInvention

[0468] The eighth generalized embodiment of the PLIIM system of thepresent invention 70 is illustrated in FIG. 5A. As shown therein, thePLIIM system 70 comprises: a housing 2 of compact construction; an area(i.e. 2-dimensional) type image formation and detection (IFD) module 55′including a 2-D electronic image detection array 55A, an area (2-D)imaging subsystem (LIS) 55B′ having a fixed focal length, a variablefocal distance, and a fixed field of view (FOV), for forming a 2-D imageof an illuminated object located within the fixed focal distance and FOVthereof and projected onto the 2-D image detection array 55A, so thatthe 2-D image detection array 55A can electronically detect the imageformed thereon and automatically produce a digital image data set 5representative of the detected image for subsequent image processing;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B, eachmounted on opposite sides of the IFD module 55′, for producing first andsecond planes of laser beam illumination 7A and 7B such that the 3-Dfield of view 10′ of the image formation and detection module 55′ isdisposed substantially coplanar with the planes of the first and secondplanar laser illumination beams 7A, 7B during object illumination andimage detection operations carried out by the PLIIM system. Whilepossible, this system configuration would be difficult to use whenpackages are moving by on a high-speed conveyor belt, as the planarlaser illumination beams would have to sweep across the package veryquickly to avoid blurring of the acquired images due to the motion ofthe package while the image is being acquired. Thus, this systemconfiguration might be better suited for a hold-under scanningapplication, as illustrated in FIG. 5D, wherein a person picks up apackage, holds it under the scanning system to allow the bar code to beautomatically read, and then manually routes the package to its intendeddestination based on the result of the scan.

[0469] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 55′, and any stationary FOV folding mirror employed in anyconfiguration of this generalized system embodiment, are fixedly mountedon an optical bench or chassis 8 so as to prevent any relative motion(which might be caused by vibration or temperature changes) between: (i)the image forming optics (e.g. imaging lens) within the image formationand detection module 55′ and any stationary FOV folding mirror employedtherewith, and (ii) each planar laser illumination module (i.e.VLD/cylindrical lens assembly) 55′ and each planar laser illuminationbeam folding/sweeping mirror employed in the PLIIM system configuration.Preferably, the chassis assembly 8 should provide for easy and securealignment of all optical components employed in the planar laserillumination arrays 6A and 6B as well as the image formation anddetection module 55′, as well as be easy to manufacture, service andrepair. Also, this generalized PLIIM system embodiment employs thegeneral “planar laser illumination” and “focus beam at farthest objectdistance (FBAFOD)” principles described above. Various illustrativeembodiments of this generalized PLIIM system will be described below.

[0470] First Illustrative Embodiment of the PLIIM System Shown in FIG.5A

[0471] The first illustrative embodiment of the PLIIM system of FIG. 5A,indicated by reference numeral 70A, is shown in FIGS. 5B1 and 5B2comprising: an image formation and detection module 55′ having animaging subsystem 55B′ with a fixed focal length imaging lens, avariable focal distance and a fixed field of view (of 3-D spatialextent), and an area (2-D) array of photo-electronic detectors 55Arealized using CCD technology (e.g. the Sony ICX085AL Progressive ScanCCD Image Sensor with Square Pixels for B/W Cameras, or the KodakKAF-4202 Series 2032(H)×2044(V) Full-Frame CCD Image Sensor) fordetecting 2-D images formed thereon by the imaging subsystem 55B′; apair of planar laser illumination arrays 6A and 6B for producing firstand second planar laser illumination beams 7A and 7B; and a pair ofplanar laser illumination beam folding/sweeping mirrors 57A and 57B,arranged in relation to the planar laser illumination arrays 6A and 6B,respectively, such that the planar laser illumination beams are foldedand swept so that the planar laser illumination beams 7A, 7B aredisposed substantially coplanar with a section of the 3-D FOV (10′) ofthe image formation and detection module 55′ during object illuminationand imaging operations carried out by the PLIIM system.

[0472] Planar laser illumination arrays 6A and 6B, each having aplurality of planar laser illumination modules 11A through 11F, and eachplanar laser illumination module being driven by a VLD driver circuit18; area-type image formation and detection module 55′; planar laserillumination beam folding/sweeping mirrors 57A and 57B, driven by motors58A and 58B, respectively; a high-resolution image frame grabber 19operably connected to area-type image formation and detection module55A, for accessing 2-D digital images of the object being illuminated bythe planar laser illumination arrays 6A and 6B during image formationand detection operations; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner. The operation of this systemconfiguration is as follows. Images detected by the low-resolution areacamera 61 are grabbed by the image frame grabber 62 and provided to thedecode image processor 21 by the system controller 22. The decode imageprocessor 21 automatically identifies and detects when a labelcontaining a bar code symbol structure has moved into the 3-D scanningfield, whereupon the high-resolution CCD detection array camera 55A isautomatically triggered by the system controller 22. At this point, theplanar laser illumination beams 12′ begin to sweep the 3-D scanningregion, images are captured by the high-resolution array 55A and thedecode image processor 21 decodes the detected bar code by a more robustbar code symbol decode software program.

[0473]FIG. 5B4 illustrates in greater detail the structure of the IFDmodule 55′ used in the PLIIM system of FIG. 5B3. As shown, the IFDmodule 55′ comprises a variable focus fixed focal length imagingsubsystem 55B′ and a 2-D image detecting array 55A mounted along an+optical bench 55D contained within a common lens barrel (not shown).The imaging subsystem 55B′ comprises a group of stationary lens elements55B1′ mounted along the optical bench before the image detecting array55A, and a group of focusing lens elements 55B2′ (having a fixedeffective focal length) mounted along the optical bench in front of thestationary lens elements 55B1′. In a non-customized application, focaldistance control can be provided by moving the 2-D image detecting array55A back and forth along the optical axis with translator 55C inresponse to a first set of control signals 55E generated by the systemcontroller 22, while the entire group of focal lens elements remainstationary. Alternatively, focal distance control can also be providedby moving the entire group of focal lens elements 55B2′ back and forthwith translator 55C in response to a first set of control signals 55Egenerated by the system controller, while the 2-D image detecting array55A remains stationary. In customized applications, it is possible forthe individual lens elements in the group of focusing lens elements55B2′ to be moved in response to control signals generated by the systemcontroller 22. Regardless of the approach taken, an IFD module 55′ withvariable focus fixed focal length imaging can be realized in a varietyof ways, each being embraced by the spirit of the present invention.

[0474] Second Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 5A

[0475] The second illustrative embodiment of the PLIIM system of FIG. 5Ais shown in FIGS. 5C1, 5C2 comprising: an image formation and detectionmodule 55′ having an imaging subsystem 55B′ with a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view, andan area (2-D) array of photo-electronic detectors 55A realized using CCDtechnology (e.g. the Sony ICX085AL Progressive Scan CCD Image Sensorwith Square Pixels for B/W Cameras, or the Kodak KAF-4202 Series2032(H)×2044(V) Full-Frame CCD Image Sensor) for detecting 2-D lineimages formed thereon by the imaging subsystem 55; a FOV folding mirror9 for folding the FOV in the imaging direction of the system; a pair ofplanar laser illumination arrays 6A and 6B for producing first andsecond planar laser illumination beams 7A and 7B; and a pair of planarlaser illumination beam folding/sweeping mirrors 57A and 57B, arrangedin relation to the planar laser illumination arrays 6A and 6B,respectively, such that the planar laser illumination beams are foldedand swept so that the planar laser illumination beams are disposedsubstantially coplanar with a section of the FOV of the image formationand detection module 55′ during object illumination and image detectionoperations carried out by the PLIIM system.

[0476] As shown in FIG. 5C2, the PLIIM system of FIG. 5C1 comprises: Asshown in FIG. 5C3, the PLIIM system 70A of FIG. 5C1 is shown in slightlygreater detail comprising: a low-resolution analog CCD camera 61 having(i) an imaging lens 61B having a short focal length so that the field ofview (FOV) thereof is wide enough to cover the entire 3-D scanning areaof the system, and its depth of field (DOF) is very large and does notrequire any dynamic focusing capabilities, and (ii) an area CCD imagedetecting array 61A for continuously detecting images of the 3-Dscanning area formed by the imaging from ambient light reflected offtarget object in the 3-D scanning field; a low-resolution image framegrabber 62 for grabbing 2-D image frames from the 2-D image detectingarray 61A at a video rate (e.g. 3- frames/second or so); planar laserillumination arrays 6A and 6B, each having a plurality of planar laserillumination modules 11A through 11F, and each planar laser illuminationmodule being driven by a VLD driver circuit 18; area-type imageformation and detection module 55′; FOV folding mirror 9; planar laserillumination beam folding/sweeping mirrors 57A and 57B, driven by motors58A and 58B, respectively; an image frame grabber 19 operably connectedto area-type image formation and detection module 55′, for accessing 2-Ddigital images of the object being illuminated by the planar laserillumination arrays 6A and 6B during image formation and detectionoperations; an image data buffer (e.g. VRAM) 20 for buffering 2-D imagesreceived from the image frame grabber 19; a decode image processor 21,operably connected to the image data buffer 20, for carrying out imageprocessing algorithms (including bar code symbol decoding algorithms)and operators on digital images stored within the image data buffer; anda system controller 22 operably connected to the various componentswithin the system for controlling the operation thereof in anorchestrated manner.

[0477]FIG. 5C3 illustrates in greater detail the structure of the IFDmodule 55′ used in the PLIIM system of FIG. 5C1. As shown, the IFDmodule 55′ comprises a variable focus fixed focal length imagingsubsystem 55B′ and a 2-D image detecting array 55A mounted along anoptical bench 55D contained within a common lens barrel (not shown). Theimaging subsystem 55B′ comprises a group of stationary lens elements55B1 mounted along the optical bench before the image detecting array55A, and a group of focusing lens elements 55B2 (having a fixedeffective focal length) mounted along the optical bench in front of thestationary lens elements 55B1. In a non-customized application, focaldistance control can be provided by moving the 2-D image detecting array55A back and forth along the optical axis with translator 55C inresponse to a first set of control signals 55E generated by the systemcontroller 22, while the entire group of focal lens elements 55B1 remainstationary. Alternatively, focal distance control can also be providedby moving the entire group of focal lens elements 55B2 back and forthwith the translator 55C in response to a first set of control signals55E generated by the system controller, while the 2-D image detectingarray 55A remains stationary. In customized applications, it is possiblefor the individual lens elements in the group of focusing lens elements55B2 to be moved in response to control signals generated by the systemcontroller. Regardless of the approach taken, the IFD module 55B′ withvariable focus fixed focal length imaging can be realized in a varietyof ways, each being embraced by the spirit of the present invention.

[0478] Applications for the Eighth Generalized Embodiment of the PLIIMSystem of the Present Invention, and the Illustrative EmbodimentsThereof

[0479] As the PLIIM systems shown in FIGS. 5A through 5C4 employ an IFDmodule having an area image detecting array and an imaging subsystemhaving variable focus (i.e. focal distance) control, such PLIIM systemsare good candidates for use in a presentation scanner application, asshown in FIG. 5D, as the variation in target object distance willtypically be less than 15 or so inches from the imaging subsystem. Inpresentation scanner applications, the variable focus (or dynamic focus)control characteristics of such PLIIM system will be sufficient toaccommodate for expected target object distance variations.

[0480] Ninth Generalized Embodiment of the PLIIM System of the PresentInvention

[0481] The ninth generalized embodiment of the PLIIM system of thepresent invention 80 is illustrated in FIG. 6A. As shown therein, thePLIIM system 80 comprises: a housing 2 of compact construction; an area(i.e. 2-dimensional) type image formation and detection (IFD) module 55′including a 2-D electronic image detection array 55A, an area (2-D)imaging subsystem (LIS) 55B″ having a variable focal length, a variablefocal distance, and a variable field of view (FOV) of 3-D spatialextent, for forming a 1-D image of an illuminated object located withinthe fixed focal distance and FOV thereof and projected onto the 2-Dimage detection array 55A, so that the 2-D image detection array 55A canelectronically detect the image formed thereon and automatically producea digital image data set 5 representative of the detected image forsubsequent image processing; and a pair of planar laser illuminationarrays (PLIAs) 6A and 6B, each mounted on opposite sides of the IFDmodule 55″, for producing first and second planes of laser beamillumination 7A and 7B such that the field of view of the imageformation and detection module 55″ is disposed substantially coplanarwith the planes of the first and second planar laser illumination beamsduring object illumination and image detection operations carried out bythe PLIIM system. While possible, this system configuration would bedifficult to use when packages are moving by on a high-speed conveyorbelt, as the planar laser illumination beams would have to sweep acrossthe package very quickly to avoid blurring of the acquired images due tothe motion of the package while the image is being acquired. Thus, thissystem configuration might be better suited for a hold-under scanningapplication, as illustrated in FIG. 5D, wherein a person picks up apackage, holds it under the scanning system to allow the bar code to beautomatically read, and then manually routes the package to its intendeddestination based on the result of the scan.

[0482] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 55″, and any stationary FOV folding mirror employed in anyconfiguration of this generalized system embodiment, are fixedly mountedon an optical bench or chassis so as to prevent any relative motion(which might be caused by vibration or temperature changes) between: (i)the image forming optics (e.g. imaging lens) within the image formationand detection module 55″ and any stationary FOV folding mirror employedtherewith, and (ii) each planar laser illumination module (i.e.VLD/cylindrical lens assembly) and each planar laser illumination beamfolding/sweeping mirror employed in the PLIIM system configuration.Preferably, the chassis assembly should provide for easy and securealignment of all optical components employed in the planar laserillumination arrays 6A and 6B as well as the image formation anddetection module 55″, as well as be easy to manufacture, service andrepair. Also, this generalized PLIIM system embodiment employs thegeneral “planar laser illumination” and “focus beam at farthest objectdistance (FBAFOD)” principles described above. Various illustrativeembodiments of this generalized PLIIM system will be described below.

[0483] First Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 6A

[0484] The first illustrative embodiment of the PLIIM system of FIG. 6Aindicated by reference numeral 8A is shown in FIGS. 6B1 and 6B2comprising: an area-type image formation and detection module 55″ havingan imaging subsystem 55B″ with a variable focal length imaging lens, avariable focal distance and a variable field of view, and an area (2-D)array of photo-electronic detectors 55A realized using CCD technology(e.g. the Sony ICX085AL Progressive Scan CCD Image Sensor with SquarePixels for B/W Cameras, or the Kodak KAF-4202 Series 2032(H)×2044(V)Full-Frame CCD Image Sensor) for detecting 2-D line images formedthereon by the imaging subsystem 55A; a pair of planar laserillumination arrays 6A and 6B for producing first and second planarlaser illumination beams 7A and 7B; and a pair of planar laserillumination beam folding/sweeping mirrors 57A and 57B, arranged inrelation to the planar laser illumination arrays 6A and 6B,respectively, such that the planar laser illumination beams are foldedand swept so that the planar laser illumination beams are disposedsubstantially coplanar with a section of the FOV of image formation anddetection module during object illumination and image detectionoperations carried out by the PLIIM system.

[0485] As shown in FIG. 6B3, the PLIIM system of FIG. 6B1 comprises: alow-resolution analog CCD camera 61 having (i) an imaging lens 61Bhaving a short focal length so that the field of view (FOV) thereof iswide enough to cover the entire 3-D scanning area of the system, and itsdepth of field (DOF) is very large and does not require any dynamicfocusing capabilities, and (ii) an area CCD image detecting array 61Afor continuously detecting images of the 3-D scanning area formed by theimaging from ambient light reflected off target object in the 3-Dscanning field; a low-resolution image frame grabber 62 for grabbing 2-Dimage frames from the 2-D image detecting array 61A at a video rate(e.g. 3- frames/second or so);planar laser illumination arrays 6A and6B, each having a plurality of planar laser illumination modules 11Athrough 11F, and each planar laser illumination module being driven by aVLD driver circuit 18; area-type image formation and detection module55B; planar laser illumination beam folding/sweeping mirrors 57A and57B; an image frame grabber 19 operably connected to area-type imageformation and detection module 55″, for accessing 2-D digital images ofthe object being illuminated by the planar laser illumination arrays 6Aand 6B during image formation and detection operations; an image databuffer (e.g. VRAM) 20 for buffering 2-D images received from the imageframe grabber 19; a decode image processor 21, operably connected to theimage data buffer 20, for carrying out image processing algorithms(including bar code symbol decoding algorithms) and operators on digitalimages stored within the image data buffer; and a system controller 22operably connected to the various components within the system forcontrolling the operation thereof in an orchestrated manner.

[0486]FIG. 6B4 illustrates in greater detail the structure of the IFDmodule 55″ used in the PLIIM system of FIG. 6B31. As shown, the IFDmodule 55″ comprises a variable focus variable focal length imagingsubsystem 55B″ and a 2-D image detecting array 55A mounted along anoptical bench 55D contained within a common lens barrel (not shown). Ingeneral, the imaging subsystem 55B″ comprises: a first group of focallens elements 55B1 mounted stationary relative to the image detectingarray 55A; a second group of lens elements 55B2, functioning as a focallens assembly, movably mounted along the optical bench in front of thefirst group of stationary lens elements 55B1; and a third group of lenselements 55B3, functioning as a zoom lens assembly, movably mountedbetween the second group of focal lens elements 55B2 and the first groupof stationary focal lens elements 55B1. In a non-customized application,focal distance control can also be provided by moving the second groupof focal lens elements 55B2 back and forth with translator 55C1 inresponse to a first set of control signals generated by the systemcontroller, while the 2-D image detecting array 55A remains stationary.Alternatively, focal distance control can be provided by moving the 2-Dimage detecting array 55A back and forth along the optical axis inresponse to a first set of control signals 55E2 generated by the systemcontroller 22, while the second group of focal lens elements 55B2 remainstationary. For zoom control (i.e. variable focal length control), thefocal lens elements in the third group 55B3 are typically moved relativeto each other with translator 55C2 in response to a second set ofcontrol signals 55E2 generated by the system controller 22. Regardlessof the approach taken in any particular illustrative embodiment, an IFDmodule with variable focus variable focal length imaging can be realizedin a variety of ways, each being embraced by the spirit of the presentinvention.

[0487] Second Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 6A

[0488] The second illustrative embodiment of the PLIIM system of FIG. 6Ais shown in FIG. 6C1 and 6C2 comprising: an image formation anddetection module 55″ having an imaging subsystem 55B″ with a variablefocal length imaging lens, a variable focal distance and a variablefield of view, and an area (2-D) array of photo-electronic detectors 55Arealized using CCD technology (e.g. the Sony ICX085AL Progressive ScanCCD Image Sensor with Square Pixels for B/W Cameras, or the KodakKAF-4202 Series 2032(H)×2044(V) Full-Frame CCD Image Sensor) fordetecting 2-D line images formed thereon by the imaging subsystem 55B″;a FOV folding mirror 9 for folding the FOV in the imaging direction ofthe system; a pair of planar laser illumination arrays 6A and 6B forproducing first and second planar laser illumination beams 7A and 7B;and a pair of planar laser illumination beam folding/sweeping mirrors57A and 57B, arranged in relation to the planar laser illuminationarrays 6A and 6B, respectively, such that the planar laser illuminationbeams are folded and swept so that the planar laser illumination beamsare disposed substantially coplanar with a section of the FOV of theimage formation and detection module during object illumination andimage detection operations carried out by the PLIIM system.

[0489] As shown in FIG. 6C2, the PLIIM system of FIGS. 6C1 and 6C2comprises: a low-resolution analog CCD camera 61 having (i) an imaginglens 61B having a short focal length so that the field of view (FOV)thereof is wide enough to cover the entire 3-D scanning area of thesystem, and its depth of field (DOF) is very large and does not requireany dynamic focusing capabilities, and (ii) an area CCD image detectingarray 61A for continuously detecting images of the 3-D scanning areaformed by the imaging from ambient light reflected off target object inthe 3-D scanning field; a low-resolution image frame grabber 62 forgrabbing 2-D image frames from the 2-D image detecting array 61A at avideo rate (e.g. 3- frames/second or so); planar laser illuminationarrays 6A and 6B, each having a plurality of planar laser illuminationmodules 11A through 11F, and each planar laser illumination module beingdriven by a VLD driver circuit 18; area-type image formation anddetection module 55A; FOV folding mirror 9; planar laser illuminationbeam folding/sweeping mirrors 57A and 57B; a high-resolution image framegrabber 19 operably connected to area-type image formation and detectionmodule 55″ for accessing 2-D digital images of the object beingilluminated by the planar laser illumination arrays 6A and 6B duringimage formation and detection operations; an image data buffer (e.g.VRAM) 20 for buffering 2-D images received from the image frame grabber19; a decode image processor 21, operably connected to the image databuffer 20, for carrying out image processing algorithms (including barcode symbol decoding algorithms) and operators on digital images storedwithin the image data buffer; and a system controller 22 operablyconnected to the various components within the system for controllingthe operation thereof in an orchestrated manner.

[0490]FIG. 6C4 illustrates in greater detail the structure of the IFDmodule 55″ used in the PLIIM system of FIG. 6C1. As shown, the IFDmodule 55″ comprises a variable focus variable focal length imagingsubsystem 55B″ and a 2-D image detecting array 55A mounted along anoptical bench 55D contained within a common lens barrel (not shown). Ingeneral, the imaging subsystem 55B″ comprises: a first group of focallens elements 55B1 mounted stationary relative to the image detectingarray 55A; a second group of lens elements 55B2, functioning as a focallens assembly, movably mounted along the optical bench in front of thefirst group of stationary lens elements 55A1; and a third group of lenselements 55B3, functioning as a zoom lens assembly, movably mountedbetween the second group of focal lens elements 55B2 and the first groupof stationary focal lens elements 55B1. In a non-customized application,focal distance control can also be provided by moving the second groupof focal lens elements 55B2 back and forth with translator 55C1 inresponse to a first set of control signals 55E1 generated by the systemcontroller 22, while the 2-D image detecting array 55A remainsstationary. Alternatively, focal distance control can be provided bymoving the 2-D image detecting array 55A back and forth along theoptical axis with translator 55C1 in response to a first set of controlsignals 55A generated by the system controller 22, while the secondgroup of focal lens elements 55B2 remain stationary. For zoom control(i.e. variable focal length control), the focal lens elements in thethird group 55B3 are typically moved relative to each other withtranslator in response to a second set of control signals 55E2 generatedby the system controller 22. Regardless of the approach taken in anyparticular illustrative embodiment, an IFD module with variable focusvariable focal length imaging can be realized in a variety of ways, eachbeing embraced by the spirit of the present invention.

[0491] Applications for the Ninth Generalized Embodiment of the PLIIMSystem of the Present Invention

[0492] As the PLIIM systems shown in FIGS. 6A through 6C4 employ an IFDmodule having an area-type image detecting array and an imagingsubsystem having variable focal length (zoom) and variable focaldistance (focus) control mechanism, such PLIIM systems are goodcandidates for use in a presentation scanner application, as shown inFIG. 6D, as the variation in target object distance will typically beless than 15 or so inches from the imaging subsystem. In presentationscanner applications, the variable focus (or dynamic focus) controlcharacteristics of such PLIIM system will be sufficient to accommodatefor expected target object distance variations. All digital imagesacquired by this PLIIM system will have substantially the same dpi imageresolution, regardless of the object's distance during illumination andimaging operations. This feature is useful in 1-D and 2-D bar codesymbol reading applications.

[0493] Tenth Generalized Embodiment of the PLIIM System of the PresentInvention, Wherein a 3-D Field of View and a Pair of Planar LaserIllumination Beams are Controllably Steered about a 3-D Scanning Region

[0494] Referring to FIGS. 6E1 through 6E4, the tenth generalizedembodiment of the PLIIM system of the present invention 90 will now bedescribed, wherein a 3-D field of view 101 and a pair of planar laserillumination beams are controllably steered about a 3-D scanning regionin order to achieve a greater region of scan coverage.

[0495] As shown in FIG. 6E2, PLIIM system of FIG. 6E1 comprises: anarea-type image formation and detection module 55′; a pair of planarlaser illumination arrays 6A and 6B; a pair of x and y axis field ofview (FOV) sweeping mirrors 91A and 91B, driven by motors 92A and 92B,respectively, and arranged in relation to the image formation anddetection module 55″; a pair of x and y axis planar laser illuminationbeam folding and sweeping mirrors 93A and 93B, driven by motors 94 and94B, respectively, and a pair of x and y planar laser illumination beamfolding and sweeping mirrors 95A and 95B, driven by motors 96A and 96B,respectively, and wherein mirrors, 93A, 93B and 95A, 95B are arranged inrelation to the pair of planar laser beam illumination beam arrays 65and 66, respectively, such that the planes of the laser illuminationbeams 7A, 7B are coplanar with a planar section of the 3-D field of view(101) of the image formation and detection module 55″ as the planarlaser illumination beams and the FOV of the IFD module 55″ aresynchronously scanned across a 3-D region of space during objectillumination and image detection operations.

[0496] As shown in FIG. 6E3, the PLIIM system of FIG. 6E2 comprises:area-type image formation and detection module 55″ having an imagingsubsystem 55B″ with a variable focal length imaging lens, a variablefocal distance and a variable field of view (FOV) of 3-D spatial extent,and an area (2-D) array of photo-electronic detectors 55A realized usingCCD technology (e.g. the Sony ICX085AL Progressive Scan CCD Image Sensorwith Square Pixels for B/W Cameras, or the Kodak KAF-4202 Series2032(H)×2044(V) Full-Frame CCD Image Sensor) for detecting 2-D imagesformed thereon by the imaging subsystem 55A; planar laser illuminationarrays, 6A, 6B; x and y axis FOV steering mirrors 91A and 91B; x and yaxis planar laser illumination beam sweeping mirrors 93A and 93B, and95A and 95B; an image frame grabber 19 operably connected to area-typeimage formation and detection module 55A, for accessing 2-D digitalimages of the object being illuminated by the planar laser illuminationarrays 6A and 6B during image formation and detection operations; animage data buffer (e.g. VRAM) 20 for buffering 2-D images received fromthe image frame grabber 19; a decode image processor 21, operablyconnected to the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.Area-type image formation and detection module 55″ can be realized usinga variety of commercially available high-speed area-type CCD camerasystems such as, for example, the KAF-4202 Series 2032(H)×2044(V)Full-Frame CCD Image Sensor, from Eastman Kodak Company-MicroelectronicsTechnology Division-Rochester, New York.

[0497]FIG. 6F4 illustrates a portion of the system 90 in FIG. 6E1,wherein the 3-D field of view (FOV) of the image formation and detectionmodule 55″ is shown steered over the 3-D scanning region of the systemusing a pair of x and y axis FOV folding mirrors 91A and 91B, which workin cooperation with the x and y axis planar laser illumination beamfolding/steering mirrors 93A and 93B and 95A and 95B to steer the pairof planar laser illumination beams 7A and 7B in a coplanar relationshipwith the 3-D FOV (101), in accordance with the principles of the presentinvention.

[0498] In accordance with the present invention, the planar laserillumination arrays 6A and 6B, the linear image formation and detectionmodule 55″, folding/sweeping FOV folding mirrors 91A and 91B, and planarlaser beam illumination folding/sweeping mirrors 93A, 93B, 95A and 95Bemployed in this system embodiment, are mounted on an optical bench orchassis so as to prevent any relative motion (which might be caused byvibration or temperature changes) between: (i) the image forming optics(e.g. imaging lens) within the image formation and detection module 55″and FOV folding/sweeping mirrors 91A, 91B employed therewith; and (ii)each planar laser illumination module (i.e. VLD/cylindrical lensassembly) and each planar laser illumination beam folding/sweepingmirror 93A, 93B, 95A and 95B employed in the PLIIM system configuration.Preferably, the chassis assembly should provide for easy and securealignment of all optical components employed in the planar laserillumination arrays 6A and 6B as well as the image formation anddetection module 55″, as well as be easy to manufacture, service andrepair. Also, this PLIIM system embodiment employs the general “planarlaser illumination” and “focus beam at farthest object distance(FBAFOD)” principles described above. Various illustrative embodimentsof this generalized PLIIM system will be described below.

[0499] First Illustrative Embodiment of the Hybrid Holographic/CCD-BasedPLIIM System of the Present Invention

[0500] In FIG. 7A, a first illustrative embodiment of the hybridholographic/CCD-based PLIIM system of the present invention 100 isshown, wherein a holographic-based imaging subsystem is used to producea wide range of discrete field of views (FOVs), over which the systemcan acquire images of target objects using a linear image detectionarray having a 2-D field of view (FOV) that is coplanar with a planarlaser illumination beam in accordance with the principles of the presentinvention. In this system configuration, it is understood that the PLIIMsystem will be supported over a conveyor belt structure which transportspackages past the PLIIM system 100 at a substantially constant velocityso that lines of scan data can be combined together to construct 2-Dimages upon which decode image processing algorithms can be performed.

[0501] As illustrated in FIG. 7A, the hybrid holographic/CCD-based PLIIMsystem 100 comprises: (i) a pair of planar laser illumination arrays 6Aand 6B for generating a pair of planar laser illumination beams 7A and7B that produce a composite planar laser illumination beam 12 forilluminating a target object residing within a 3-D scanning volume; aholographic-type cylindrical lens 101 is used to collimate the rays ofthe planar laser illumination beam down onto the conveyor belt surface;and a motor-driven holographic imaging disc 102, supporting a pluralityof transmission-type volume holographic optical elements (HOE) 103, astaught in U.S. Pat. No. 5,984,185, incorporated herein by reference.Each HOE 103 on the imaging disc 102 has a different focal length, whichis disposed before a linear (1-D) CCD image detection array 3A. Theholographic imaging disc 102 and image detection array 3A function as avariable-type imaging subsystem that is capable of detecting images ofobjects over a large range of object distances within the 3-D FOV (10″)of the system while the composite planar laser illumination beam 12illuminates the object.

[0502] As illustrated in FIG. 7A, the PLIIM system 100 furthercomprises: an image frame grabber 19 operably connected to linear-typeimage formation and detection module 3A, for accessing 1-D digitalimages of the object being illuminated by the planar laser illuminationarrays 6A and 6B during object illumination and imaging operations; animage data buffer (e.g. VRAM) 20 for buffering 2-D images received fromthe image frame grabber 19; a decode image processor 21, operablyconnected to the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.

[0503] As shown in FIG. 7B, a coplanar relationship exists between theplanar laser illumination beam(s) produced by the planar laserillumination arrays 6A and 6B, and the variable field of view (FOV) 10″produced by the variable holographic-based focal length imagingsubsystem described above. The advantage of this hybrid system design isthat it enables the generation of a 3-D image-based scanning volumehaving multiple depths of focus by virtue of the holographic-basedvariable focal length imaging subsystem employed in the PLIIM system.

[0504] Second Illustrative Embodiment of the HybridHolographic/CCD-Based PLIIM System of the Present Invention

[0505] In FIG. 8A, a second illustrative embodiment of the hybridholographic/CCD-based PLIIM system of the present invention 100′ isshown, wherein a holographic-based imaging subsystem is used to producea wide range of discrete field of views (FOVs), over which the systemcan acquire images of target objects using an area-type image detectionarray having a 3-D field of view (FOV) that is coplanar with a planarlaser illumination beam in accordance with the principles of the presentinvention. In this system configuration, it is understood that the PLIIMsystem 100′ can used in a holder-over type scanning application,hand-held scanner application, or presentation-type scanner.

[0506] As illustrated in FIG. 8A, the hybrid holographic/CCD-based PLIIMsystem 101′ comprises: (i) a pair of planar laser illumination arrays 6Aand 6B for generating a pair of planar laser illumination beams 7A and7B; a pair of planar laser illumination beam folding/sweeping mirrors37A′ and 37B′ for folding and sweeping the planar laser illuminationbeams through the 3-D field of view of the imaging subsystem; aholographic-type cylindrical lens 101 for collimating the rays of theplanar laser illumination beam down onto the conveyor belt surface; anda motor-driven holographic imaging disc 102, supporting a plurality oftransmission-type volume holographic optical elements (HOE) 103, as thedisc is rotated about its rotational axis. Each HOE 103 on the imagingdisc has a different focal length, and is disposed before an area (2-D)type CCD image detection array 55A. The holographic imaging disc 102 andimage detection array 55A function as a variable-type imaging subsystemthat is capable of detecting images of objects over a large range ofobject (i.e. working) distances within the 3-D FOV (10″) of the systemwhile the composite planar laser illumination beam 12 illuminates theobject.

[0507] As illustrated in FIG. 8A, the PLIIM system 101′ furthercomprises: an image frame grabber 19 operably connected to an area-typeimage formation and detection module 55″, for accessing 2-D digitalimages of the object being illuminated by the planar laser illuminationarrays 6A and 6B during object illumination and imaging operations; animage data buffer (e.g. VRAM) 20 for buffering 2-D images received fromthe image frame grabber 19; a decode image processor 21, operablyconnected to the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.

[0508] As shown in FIG. 8B, a coplanar relationship exists between theplanar laser illumination beam(s) produced by the planar laserillumination arrays 6A and 6B, and the variable field of view (FOV) 10″produced by the variable holographic-based focal length imagingsubsystem described above. The advantage of this hybrid system design isthat it enables the generation of a 3-D image-based scanning volumehaving multiple depths of focus by virtue of the holographic-basedvariable focal length imaging subsystem employed in the PLIIM system.

[0509] First Illustrative Embodiment of the Unitary PackageIdentification and Dimensioning System of the Present InventionEmbodying a PLIIM Subsystem of the Present Invention and a LADAR-BasedImaging, Detecting and Dimensioning Subsystem

[0510] Referring now to FIGS. 9 and 10, a unitary package identificationand dimensioning system of the first illustrated embodiment 120 will nowbe described in detail.

[0511] As shown in FIG. 10, the unitary system 120 of the presentinvention comprises an integration of subsystems, contained within asingle housing of compact construction supported above the conveyor beltof a high-speed conveyor subsystem 121, by way of a support frame orlike structure. In the illustrative embodiment, the conveyor subsystem121 has a conveyor belt width of at least 48 inches to support one ormore package transport lanes along the conveyor belt. As shown in FIG.10, the unitary system comprises four primary subsystem components,namely: (1) a LADAR-based package imaging, detecting and dimensioningsubsystem 122 capable of collecting range data from objects on theconveyor belt using a pair of multi-wavelength (i.e. containing visibleand IR spectral components) laser scanning beams projected at differentangular spacing as taught in copending U.S. application Ser. No.09/327,756 filed Jun. 7, 1999, supra; and International PCT ApplicationNo. PCT/US00/15624 filed Dec. 7, 2000, incorporated herein by reference;(2) a PLIIM-based bar code symbol reading subsystem 25′ for producing a3-D scanning volume above the conveyor belt, for scanning bar codes onpackages transported therealong; (3) an input/output subsystem 127 formanaging the inputs to and output from the unitary system; and (4) adata management computer 129 with a graphical user interface (GUI) 130,for realizing a data element queuing, handling and processing subsystem131, as well as other data and system management functions.

[0512] As shown in FIG. 10, the package imaging, detecting anddimensioning subsystem 122 comprises a number of subsystems integratedtherewithin as shown, namely: a package velocity measurement subsystem123, for measuring the velocity of transported packages by analyzingrange data maps generated by the different scanning beams, using theinventive methods disclosed in International PCT Application No.PCT/US00/15624 filed Dec. 7, 2000; a package-in-the-tunnel (PITT)indication subsystem 125, for automatically detecting the presence ofeach package moving through the scanning volume by reflecting a portionof one of the laser scanning beams across the width of the conveyor beltin a retro-reflective manner and then analyzing the return signal usingfirst derivative and thresholding techniques disclosed in InternationalPCT Application No. PCT/US00/15624 filed Dec. 7, 2000; a package (x-y)height/width/length dimensioning (or profiling) subsystem 124,integrated within subsystem 122, for producing x, y, z profile data setsfor detected packages; and a package-out-of-the-tunnel (POOT) indicationsubsystem 125, integrated within subsystem 122, realized usingpredictive techniques based on the output of the PITT indicationsubsystem 125, for automatically detecting the presence of packagesmoving out of the scanning volume. As shown in FIG. 10, the unitarysystem 120 is adapted to receive data inputs from a number of inputdevices including, for example: weighing-in-motion subsystem 132 forweighing packages as they are transported along the conveyor belt; anRF-tag reading subsystem for reading RF tags on packages as they aretransported along the conveyor belt; etc.

[0513] The primary function of subsystem 122 is to measure dimensionalcharacteristics of packages passing through the scanning volume, andproduce package dimension data for each dimensioned package. The primaryfunction of scanning subsystem 25′ is to read bar code symbols ondimensioned packages and produce package identification datarepresentative of each identified package. The primary function of theI/O subsystem 127 is to transport package dimension data elements andpackage identification data elements to the data element queuing,handling and processing subsystem 131. The primary function of the dataelement queuing, handling and processing subsystem 131 is to link eachpackage dimension data element with its corresponding packageidentification data element, and to transport such data element pairs toan appropriate host system for subsequent use. By embodying subsystem25′ and LDIP subsystem 122 within a single housing 121, an ultra-compactdevice is provided that can both dimension and identify packages movingalong the package conveyor without requiring the use of any externalperipheral input devices, such as tachometers, light-curtains, etc.

[0514] Second Illustrative Embodiment of the Unitary PackageIdentification and Dimensioning System of the Present InventionEmbodying a PLIIM Subsystem of the Present Invention and a LADAR-BasedImaging Detecting and Dimensioning Subsystem

[0515] Referring now to FIGS. 11 and 12, a unitary packageidentification and dimensioning system of the second illustratedembodiment 140 will now be described in detail.

[0516] As shown in FIG. 11, the unitary system 140 of the presentinvention comprises an integration of subsystems, contained within asingle housing of compact construction supported above the conveyor beltof a high-speed conveyor subsystem 141, by way of a support frame orlike structure. In the illustrative embodiment, the conveyor subsystem141 has a conveyor belt width of at least 48 inches to support one ormore package transport lanes along the conveyor belt. As shown in FIG.11, the unitary system comprises four primary subsystem components,namely: (1) a LADAR-based package imaging, detecting and dimensioningsubsystem 122 capable of collecting range data from objects on theconveyor belt using a pair of multi-wavelength (i.e. containing visibleand IR spectral components) laser scanning beams projected at differentangular spacing as taught in copending U.S. application Ser. No.09/327,756 filed Jun. 7, 1999, supra; and International PCT ApplicationNo. PCT/US00/15624 filed Dec. 7, 2000, incorporated herein by reference;(2) a PLIIM-based bar code symbol reading subsystem 25″, shown in FIGS.6C1 through 6D5, for producing a 3-D scanning volume above the conveyorbelt, for scanning bar codes on packages transported therealong; (3) aninput/output subsystem 127 for managing the inputs to and outputs fromthe unitary system; and (4) a data management computer 129 with agraphical user interface (GUI) 130, for realizing a data elementqueuing, handling and processing subsystem 131, as well as other dataand system management functions.

[0517] As shown in FIG. 11, the package imaging, detecting anddimensioning subsystem 122 comprises a number of subsystems integratedtherewithin as shown, namely: a package velocity measurement subsystem123, for measuring the velocity of transported packages by analyzingrange data maps generated by the different scanning beams, using theinventive methods disclosed in International PCT Application No.PCT/US00/15624 filed Dec. 7, 2000; a package-in-the-tunnel (PITT)indication subsystem 125, for automatically detecting the presence ofeach package moving through the scanning volume by reflecting a portionof one of the laser scanning beams across the width of the conveyor beltin a retro-reflective manner and then analyzing the return signal usingfirst derivative and thresholding techniques disclosed in InternationalPCT Application No. PCT/US00/15624 filed Dec. 7, 2000; a package (x-y)height/width/length dimensioning (or profiling) subsystem 124,integrated within subsystem 122, for producing x, y, z profile data setsfor detected packages; and a package-out-of-the-tunnel (POOT) indicationsubsystem 125, integrated within subsystem 122, realized usingpredictive techniques based on the output of the PITT indicationsubsystem 125, for automatically detecting the presence of packagesmoving out of the scanning volume. As shown in FIG. 10, the unitarysystem 120 is adapted to receive data inputs from a number of inputdevices including, for example: weighing-in-motion subsystem 132 forweighing packages as they are transported along the conveyor belt; anRF-tag reading subsystem for reading RF tags on packages as they aretransported along the conveyor belt; etc.

[0518] The low-resolution CCD camera 61 (having 640×640 pixels) in PLIIMsubsystem 25″ is used to locate the x,y position of bar code labels onscanned packages using ambient illumination to form images on thelow-resolution array 61A therewithin. When the low-resolution CCD areaarray 61A detects a bar code symbol on a package label, then the systemcontroller 22 triggers the high-resolution CCD image detector 55A andthe planar laser illumination arrays 6A and 6B so as to capture 2-Dimages of the high-resolution image detector's 3-D field of view 10′.The focal distance of the imaging subsystem of the high resolution imageformation and detection module 55″ is controlled by package heightcoordinate information acquired by the LDIP subsystem 122.High-resolution scan data collected from 2-D image detector 55A is thendecode processed to read the bar code symbol within the detected packagelabel in a fully automated manner without human intervention. In allother respects, the unitary system 140 shown in FIG. 11 is similar tothe system 120 shown in FIG. 9. By embodying subsystem 25″ and LDIPsubsystem 122 within a single housing 141, an ultra-compact device isprovided that can both dimension and identify packages moving along thepackage conveyor using a low-resolution CCD imaging device to detectpackage labels, and then use such detected label information to activatethe high-resolution CCD imaging device 25″ to acquire images of thedetected label for high performance decode processing.

[0519] Third Illustrative Embodiment of the Unitary PackageIdentification and Dimensioning System of the Present InventionEmbodying a PLIIM Subsystem of the Present Invention and a LADAR-BasedImaging, Detecting and Dimensioning Subsystem

[0520] In FIG. 13, a third illustrative embodiment of the unitarypackage dimensioning and identification system of the present invention160 is shown mounted above a high-speed conveyor belt structure. Asillustrated in FIGS. 14A and 14B, unitary system 160 embodies the PLIIMsubsystem 25′ of FIGS. 3E1-3E8 as well as the laser dimensioning andprofiling (LDIP) subsystem 122 within a single housing 161 of compactconstruction. Unitary system 160 is functionally identical to theunitary system 140 described above, expect that system 160 is packagedin the specially designed dual-compartment housing design shown in FIGS.14A, 14B, and 15 to be described in detail below.

[0521] As shown in FIG. 14A, the PLIIM subsystem 25″ is mounted within afirst optically compartment 162 formed in system housing 161 usingoptically opaque wall structures, whereas the LDIP subsystem 122 andbeam folding mirror 163 are mounted within a second optically isolatedcompartment 164 formed therein below the first compartment 162. Bothoptically isolated compartments are realized using optically opaque wallstructures well known in the art. As shown in FIG. 15, a first set ofspatially registered light transmission apertures 165A1, 165A2 and 165A3are formed through the bottom panel of the first compartment 162, inspatial registration with the transmission apertures formed 29A′, 28′,29B′ in subsystem 25″. Below light transmission apertures 165A1, 165A2and 165A3, there is formed a completely opened light transmissionaperture 165B, defined by vertices EFBC, so as to allow laser light toexit and enter the first compartment 162 during system operation. Ahingedly connected panel 169 is provided on the side opening of thesystem housing 161, defined by vertices ABCD. The function of thishinged panel 169 is to enable authorized personnel to access theinterior of the housing and clean the glass windows provided over thelight transmission apertures 29A′, 28′, 29B′ in spatial registrationwith apertures 165A1, 165A2 and 165A3, respectively. This is animportant consideration in most industrial scanning environments.

[0522] As shown in FIGS. 14A, the LDIP subsystem 122 is mounted withinthe second compartment 164, along with beam folding mirror 163 directedtowards a second light transmission aperture 166 formed in the bottompanel of the second compartment 164, in an optically isolated mannerfrom the first set of light transmission apertures 165A1, 165A2 and165A3. The function of the beam folding mirror 163 is to enable the LDIPsubsystem 122 to project its dual amplitude-modulated laser beams 167out of its housing, off beam folding mirror 163, and towards a targetobject to be dimensioned and profiled. Also, this light transmissionaperture 166 enables reflected laser return light to be collected anddetected off the illuminated target object.

[0523]FIG. 16 shows the unitary (PLIIM-based) package dimensioning andidentification system of the third illustrative embodiment of thepresent invention. As shown, the various information signals aregenerated by the LDIP subsystem, and provided to the camera control(computer) subsystem). The Camera Control Computer generates digitalcamera control signals which are provided to the image formation anddetection (IFD subsystem (i.e. “camera”) so that the system can carryout its diverse functions in an integrated manner, including (1)capturing digital images having (i) square pixels (i.e. 1:1 aspectratio) independent of package height or velocity, (ii) significantlyreduced speckle-noise levels, and (iii) constant image resolutionmeasured in dots per inch (DPI) independent of package height orvelocity and without the use of costly telecentric optics employed byprior art systems, (2) automatic cropping of captured images so thatonly regions of interest reflecting the package or package label aretransmitted to either a image-processing based 1-D or 2-D bar codesymbol decoder or an optical character recognition (OCR) imageprocessor, and (3) automatic image lifting operations for supportingother package management operations carried out by the end-user. ThePLIIM subsystem” generates digital images of the target object passingwithin the subsystem's field of view (FOV) and these images are thenprocessed to decode bar code symbols represented within the images andproduce package identification data. Each such package identificationdata element is then provided to the Camera Control Computer or othercomputer within the unit for linking with a corresponding packagedimension data element, as described hereinabove. Optionally, acquireddigital images of packages passing beneath the PLIIM subsystem 25″ canbe processed in other ways to extract other relevant features of thepackage which might be useful in package identification, tracking,routing and/or dimensioning purposes.

[0524]FIG. 17 shows a fourth illustrative embodiment of the unitarypackage dimensioning and identification system of the present invention.As shown, this system embodies the PLIIM subsystem of the presentinvention as well as the laser dimensioning and profiling (LDIP)subsystem within a single housing of compact construction.

[0525]FIG. 18A shows the PLIIM subsystem and its components containedwithin a first optically isolated compartment formed the unitary systemhousing, and the LDIP subsystem contained within a second opticallyisolated compartment formed therein. A first set of spatially registeredlight transmission apertures are formed through the panels of both thefirst and second cavities to enable the PLIIM system to project itsplanar laser illumination beams towards a target object to beilluminated and collect and receive laser return light off theilluminated object. A second set of light transmission apertures,optically isolated from the first set of light transmission apertures,are formed in the second cavity to enable the LDIP subsystem to projectits dual amplitude-modulated laser beams towards a target object to bedimensioned and profiled, and also to collect and receive laser returnlight reflected off the illuminated target object.

[0526]FIG. 18B shows the spatial layout of the various optical andelectro-optical components mounted on the optical bench of the PLIIMsubsystem installed within the first cavity of the system housing.

[0527] As shown in FIG. 18C, an illustrative implementation of theimaging subsystem contained in the image formation and detection (IFD)module employed in the PLIIM system of FIG. 17, comprises: a stationarylens system mounted before the stationary linear (CCD-type) imagedetection array; a first movable lens system for stepped movementrelative to the stationary lens system during image zooming operations;and a second movable lens system for stepped movements relative to thefirst movable lens system and the stationary lens system during imagefocusing operations. The first movable lens system employs a zoom lensgroup translator to move the zoom lens group to a position specified bythe Camera Control Computer shown in FIG. 20. The second movable lenssystem employs a focus lens group translator to move the focus lensgroup to a position specified by the Camera Control Computer shown inFIG. 20.

[0528]FIG. 19 shows a unitary (PLIIM-based) package dimensioning andidentification system of the fourth illustrative embodiment. As showntherein, the various information signals are generated by the LDIPsubsystem, and provided to the Camera Control (Computer) Subsystem. TheCamera Control Computer generates digital camera control signals whichare provided to the image formation and detection (IFD subsystem (i.e.“camera”) so that the system can carry out its diverse functions in anintegrated manner, including (1) capturing digital images having (i)square pixels (i.e. 1:1 aspect ratio) independent of package height orvelocity, (ii) significantly reduced speckle-noise levels, and (iii)constant image resolution measured in dots per inch (DPI) independent ofpackage height or velocity and without the use of costly telecentricoptics employed by prior art systems, (2) automatic cropping of capturedimages so that only regions of interest reflecting the package orpackage label are transmitted to either a image-processing based 1-D or2-D bar code symbol decoder or an optical character recognition (OCR)image processor, and (3) automatic image lifting operations forsupporting other package management operations carried out by theend-user.

[0529]FIG. 20 illustrates the system architecture of the unitary(PLIIM-based) package dimensioning and identification systems of thethird and fourth illustrative embodiments shown in FIGS. 13 and 17. Asshown therein, a Real-Time Package Height Profiling And Edge DetectionProcessing Module is employed within the LDIP subsystem to automaticallyprocess raw data received by the LDIP subsystem and generate, as output,time-stamped data sets that are transmitted to the Camera Control(Computer) Subsystem. In turn, the Camera Control (Computer) Subsystemautomatically processes the received time-stamped data sets andgenerates real-time camera control signals that drive the focus and zoomlens group translators within a high-speed Auto-Focus/Auto-Zoom DigitalCamera Subsystem (i.e. the IFD module) so that the camera subsystemautomatically captures digital images having (1) square pixels (i.e. 1:1aspect ratio) independent of package height or velocity, (2)significantly reduced speckle-noise levels, and (3) constant imageresolution measured in dots per inch (DPI) independent of package heightor velocity.

[0530]FIG. 21 sets forth a flow chart describing the primary dataprocessing operations that are carried out by the Real-Time PackageHeight Profiling And Edge Detection Processing Module within the LDIPsubsystem employed in the PLIIM-based systems shown in FIGS. 13 and 17.As illustrated in FIG. 21, each sampled row of raw range data collectedby the LDIP subsystem is processed to produce a data set (containinginformation data elements representative of the current time-stamp, thecurrent package height, the current position of the left and right edgesof the package edges, and the current package velocity) which is thentransmitted to the Camera Control (Computer) Subsystem for processingand generation of real-time camera control signals that are transmittedto the Auto-Focus/Auto-Zoom Digital Camera Subsystem.

[0531]FIG. 22 sets forth a flow chart describing the primary dataprocessing operations that are carried out by the Real-Time Package EdgeDetection Processing Method performed by the Real-Time Package HeightProfiling And Edge Detection Processing Module within the LDIP subsystemof PLIIM-based systems shown in FIGS. 13 and 17. This method isindicated at Block D in FIG. 21 is executed by the Real-Time PackageHeight Profiling And Edge Detection Processing Module.

[0532]FIG. 23 schematically illustrates the Real-Time Package HeightProfiling Method carried out in the flow chart of FIG. 21, and theReal-Time Package Edge Detection Method carried out in the flow chart ofFIG. 22. Notably, these processes are carried out for each sampled rowof raw data collected by the LDIP subsystem and therefore, does not relyon the results computed by the computational-based package dimensioningprocesses carried out in the LDIP subsystem, described in great detailin copending U.S. application Ser. No. 09/327,756 filed Jun. 7, 1999,and incorporated herein reference in its entirety.

[0533]FIGS. 24A and 24B describe the Real-Time Camera Control Processthat is carried out within the Camera Control Computer Subsystememployed within the PLIIM-based systems of FIGS. 13 and 17. Asillustrated in FIGS. 24A and 24B, this control process has multiplethreads that are carried out simultaneously each data processing cycle(i.e. each time a new data set is received from the Real-Time PackageHeight Profiling And Edge Detection Processing Module within the LDIPsubsystem. As illustrated in this flow chart, the data elementscontained in each received data set are automatically processed withinthe Camera Control (Computer) Subsystem in the manner described in theflow chart, and at the end of each data set processing cycle, generatesreal-time camera control signals that drive the focus and zoom lensgroup translators within a high-speed Auto-Focus/Auto-Zoom DigitalCamera Subsystem (i.e. the IFD module) so that the camera subsystemautomatically captures digital images having (1) square pixels (i.e. 1:1aspect ratio) independent of package height or velocity, (2)significantly reduced speckle-noise levels, and (3) constant imageresolution measured in dots per inch (DPI) independent of package heightor velocity.

[0534]FIG. 25 illustrates the structure of the Package Data Bufferemployed by the Real-Time Package Height Profiling And Edge DetectionProcessing Module illustrated in FIGS. 20, 21, 22, and 23. As showntherein, each current raw data set received by the Real-Time PackageHeight Profiling And Edge Detection Processing Module is buffered in arow of the Package Data Buffer. Each data element in the raw data set isassigned a fixed column index and variable row index which increments asthe raw data set is shifted one index unit as each new incoming raw dataset is received into the Package Data Buffer.

[0535]FIG. 26. Illustrates the structure of the Camera Pixel Data Bufferemployed by the Auto-Focus/Auto-Zoom Digital Camera Subsystem shown inFIG. 20. As shown, each pixel element in each captured image frame isstored in a storage cell of the Camera Pixel Data Buffer, assigned aunique set of pixel indices (i,j).

[0536]FIG. 27 shows an exemplary Zoom and Focus Lens Group PositionLook-Up Table associated with the Auto-Focus/Auto-Zoom Digital CameraSubsystem and which is used by the Camera Control (Computer) Subsystemof the illustrative embodiment. For a given package height detected bythe Real-Time Package Height Profiling And Edge Detection ProcessingModule, the Camera Control Computer (at Block E in FIG. 24B) uses theLook-Up Table to determine the precise positions to which the focus andzoom lens groups must be moved by generating and supplying real-timecamera control signals to the focus and zoom lens group translatorswithin a high-speed Auto-Focus/Auto-Zoom Digital Camera Subsystem (i.e.the IFD module) so that the camera subsystem automatically capturesfocused digital images having (1) square pixels (i.e. 1:1 aspect ratio)independent of package height or velocity, (2) significantly reducedspeckle-noise levels, and (3) constant image resolution measured in dotsper inch (DPI) independent of package height or velocity.

[0537]FIG. 28 shows a graphical plot of the focus and zoom lens movementcharacteristics associated with the zoom and lens groups employed in theillustrative embodiment of the Auto-Focus/Auto-Zoom Digital CameraSubsystem. Notably, these characteristics were used to generate the Zoomand Focus Lens Group Position Look-Up Table of FIG. 27. As shown in thisgraphical chart, for a given detected package height, the position ofthe focus and zoom lens group relative to the Camera's working distanceis obtained by finding the points along these characteristics at thespecified working distance (i.e. detected package height).

[0538]FIG. 29 shows an exemplary Photo-integration Time Period Look-UpTable associated with CCD image detection array employed in theAuto-Focus/Auto-Zoom Digital Camera Subsystem of the PLIIM-based system.As shown at Block K in FIG. 24B, for a given detected package height andpackage velocity, the Camera Control Computer uses this Look-Up Table todetermine the precise photo-integration time period for the CCD imagedetection elements employed within the Auto-Focus/Auto-Zoom DigitalCamera Subsystem (i.e. the IFD module) so that the camera subsystemautomatically captures focused digital images having (1) square pixels(i.e. 1:1 aspect ratio) independent of package height or velocity, (2)significantly reduced speckle-noise levels, and (3) constant imageresolution measured in dots per inch (DPI) independent of package heightor velocity.

[0539] As shown at Blocks L through N in FIG. 24B, the Camera ControlComputer also performs, automatically, cropping of captured images sothat only regions of interest (ROI) reflecting the package or packagelabel are transmitted to either the image-processing based 1-D or 2-Dbar code symbol decoder and/or an optical character recognition (OCR)image processor within the PLIIM-based system described above. This ROIcropping function serves to selectively transmit only those image pixelswithin the Camera Pixel Buffer of FIG. 26, having pixel indices (i,j)which spatially correspond to the (row,column) indices in the PackageData Buffer of FIG. 25. The data processing operations described atBlock L, M and N, in particular, determine such correspondence and theresulting corresponding pixel indices are used to transfer (to theimage-processing based 1-D or 2-D bar code symbol decoder and/or anoptical character recognition (OCR) image processor) only those imagepixels that correspond to the region of interest bounded by the(row,column) indices embracing the spatial boundaries of the packagewhile being imaged by the Auto-Focus/Auto-Zoom Digital Camera Subsystem(i.e. the IFD module). This inventive filtering operation reduces thetransmission image pixels to the bar code symbol decoder and/or OCRprocessor which do not contain information about the identity, originand/or destination of the package moving along the conveyor belt.

[0540]FIG. 30 shows a four-sided tunnel-type package identification anddimensioning (PID) system that has been constructed by arranging fourPLIIM-based PID units shown in FIGS. 13 and 17 about a high-speedpackage conveyor belt subsystem. In this system, the LDIP subsystem inthe top PID unit is configured to dimension packages transported alongthe belt, while the bottom PID unit is arranged to view packages througha small gap between conveyor belt sections, and all of the PID units areoperably connected to the Ethernet control hub of a local area network(LAN). FIG. 31 shows the tunnel-type system of FIG. 30 embedded within afirst-type LAN having a Ethernet control hub. FIG. 32 shows thetunnel-type system of FIG. 30 embedded within a second-type LAN having aEthernet control hub and a Ethernet data switch.

[0541] Applications of the Unitary Package Identification andDimensioning System of the Present Invention

[0542] In general, the package identification and measuring systems ofthe present invention can be installed in package routing hubs, shippingterminals, airports, factories, and the like. There of course will benumerous other applications for such systems as new situations arise,and the capabilities of such systems become widely known to the generalpublic.

[0543] Modifications of the Illustrative Embodiments

[0544] While each embodiment of the PLIIM system of the presentinvention disclosed herein has employed a pair of planar laserillumination arrays, it is understood that in other embodiments of thepresent invention, only a single PLIA may be used, whereas in otherembodiments three or more PLIAs may be used depending on the applicationat hand.

[0545] While the illustrative embodiments disclosed herein have employedelectronic-type imaging detectors (e.g. 1-D and 2-D CCD-type imagesensing/detecting arrays) for the clear advantages that such devicesprovide in bar code and other photo-electronic scanning applications, itis understood, however, that photo-optical and/or photo-chemical imagedetectors/sensors (e.g. optical film) can be used to practice theprinciples of the present invention disclosed herein.

[0546] While the package conveyor subsystems employed in theillustrative embodiments have utilized belt or roller structures totransport packages, it is understood that this subsystem can be realizedin many ways, for example: using trains running on tracks passingthrough the laser scanning tunnel; mobile transport units runningthrough the scanning tunnel installed in a factory environment;robotically-controlled platforms or carriages supporting packages,parcels or other bar coded objects, moving through a laser scanningtunnel subsystem.

[0547] While the various embodiments of the package identification andmeasuring system hereof have been described in connection with linear(1-D) and 2-D code symbol scanning applications, it should be clear,that the system and methods of the present invention are equally suitedfor scanning alphanumeric characters (e.g. textual information) inoptical character recognition (OCR) applications, as taught in U.S. Pat.No. 5,727,081 to Burges, et al, incorporated herein by reference, andscanning graphical images as practiced in the graphical scanning arts.

[0548] It is understood that the laser scanning systems, modules,engines and subsystems of the illustrative embodiments may be modifiedin a variety of ways which will become readily apparent to those skilledin the art, and having the benefit of the novel teachings disclosedherein. All such modifications and variations of the illustrativeembodiments thereof shall be deemed to be within the scope and spirit ofthe present invention as defined by the claims to Invention appendedhereto.

Claims to invention:
 1. A system for illuminating an object and formingan image thereof, comprising: an image formation and detection modulehaving a field of view (FOV) focused at an image detecting array; and aplanar laser illumination array for producing a planar laserillumination beam having substantially-planar spatial distributioncharacteristics that extend through the field of view (FOV) of saidimage formation and detection module, so that laser light reflected offan object illuminated by said planar laser illumination beam is focusedalong said field of view and onto said image detecting array to form animage of said illuminated object.
 2. The system of claim 1, wherein saidplanar laser illumination beam array comprises an plurality of planarlaser illumination modules, wherein each said planar laser illuminationmodule comprises a visible laser diode (VLD), a focusing lens, and acylindrical optical element arranged therewith to produce a planar laserillumination beam component.
 3. The system of claim 2, wherein theindividual planar laser illumination beam components produced from saidplurality of planar laser illumination modules are optically combined toproduce a composite substantially planar laser illumination beam havingsubstantially uniform power density characteristics over the entirespatial extend thereof and thus the working range of the system.
 4. Thesystem of claim 3, wherein each planar laser illumination beam componentis focused so that the minimum beam width thereof occurs at a point orplane which is the farthest or maximum object distance at which thesystem is designed to acquire images, thereby compensating for decreasesin the power density of the incident planar laser illumination beam dueto the fact that the width of the planar laser illumination beamincreases in length for increasing object distances away from theimaging optics.
 5. A method of illuminating an object and forming animage thereof, comprising the steps of: (a) providing a field of view(FOV) focused at an image detecting array; and (b) producing a planarlaser illumination beam having substantially-planar spatial distributioncharacteristics that extend through said field of view (FOV) so thatlaser light reflected off an object illuminated by said planar laserillumination beam is focused along said field of view and onto saidimage detecting array to form an image of said illuminated object. 6.The method of claim 5, wherein said step (b) comprise: producing aplurality of laser beams from a plurality of visible laser diodes(VLDs); focusing each said laser beam through a focusing lens, andexpanding the focused laser beam through a cylindrical optical elementso as to produce a substantially planar laser illumination beamcomponent; optically combining the plurality of planar laserillumination beam components produce a composite substantially planarlaser illumination beam having substantially uniform power densitycharacteristics over the entire spatial extend thereof and thus theworking range of the system.
 7. The method of claim 6, wherein eachplanar laser illumination beam component is focused so that the minimumbeam width thereof occurs at a point or plane which is the farthest ormaximum object distance at which the system is designed to acquireimages, thereby compensating for decreases in the power density of theincident planar laser illumination beam due to the fact that the widthof the planar laser illumination beam increases in length for increasingobject distances away from the imaging optics.
 8. A system forilluminating the surface of objects using a linear array of laser lightemitting devices configured together to produce a substantially planarbeam of laser illumination which extends in substantially the same planeas the field of view of the linear array of electronic image detectioncells of the system, along at least a portion of its optical path withinits working distance,
 9. The system of claim 8, wherein the linear arrayof electronic image detection cells are realized using charge-coupleddevice (CCD) technology.
 10. A system for producing digital images ofobjects using a visible laser diode array for producing a planar laserillumination beam for illuminating the surfaces of such objects, andalso an electronic image detection array for detecting laser lightreflected off the illuminated objects during illumination and imagingoperations.
 11. A system for illuminating the surfaces of object to beimaged, using an array of planar laser illumination arrays which employVLDs that are smaller, and cheaper, run cooler, draw less power, havelonger lifetimes, and require simpler optics (because their frequencybandwidths are very small compared to the entire spectrum of visiblelight).
 12. A system for illuminating the surfaces of objects to beimaged, wherein the VLD concentrates all of its output power into a thinlaser beam illumination plane which spatially coincides exactly with thefield of view of the imaging optics of the system, so very little lightenergy is wasted.
 13. A laser illumination and imaging system, whereinthe working distance of the system can be easily extended by simplychanging the beam focusing and imaging optics, and without increasingthe output power of the visible laser diode (VLD) sources employedtherein.
 14. A laser illumination and imaging system, wherein eachplanar laser illumination beam is focused so that the minimum widththereof (e.g. along its non-spreading direction) occurs at a point orplane which is the farthest object distance at which the system isdesigned to capture images.
 15. A laser illumination and imaging system,wherein a fixed focal length imaging subsystem is employed, and thelaser beam focusing technique of the present invention helps compensatefor decreases in the power density of the incident planar illuminationbeam due to the fact that the width of the planar laser illuminationbeam for increases increasing distances away from the imaging subsystem.16. A laser illumination and imaging system, wherein a variable focallength (i.e. zoom) imaging subsystem is employed, and the laser beamfocusing technique of the present invention helps compensate for (i)decreases in the power density of the incident illumination beam due tothe fact that the width of the planar laser illumination beam (i.e.beamwidth) along the direction of the beam's planar extent increases forincreasing distances away from the imaging subsystem, and (ii) any 1/r²type losses that would typically occur when using the planar laserillumination beam.
 17. A laser illumination and imaging system, whereinscanned objects need only be illuminated along a single plane which iscoplanar with a planar section of the field of view of the imageformation and detection module being used in the system.
 18. A laserillumination and imaging system, wherein low-power, light-weight,high-response, ultra-compact, high-efficiency solid-state illuminationproducing devices, such as visible laser diodes (VLDs), are used toselectively illuminate ultra-narrow sections of a target object duringimage formation and detection operations, in contrast with high-power,low-response, heavy-weight, bulky, low-efficiency lighting equipment(e.g. sodium vapor lights) required by prior art illumination and imagedetection systems.
 19. A laser illumination and imaging system, whereinthe planar laser illumination technique of the present invention enableshigh-speed modulation of the planar laser illumination beam, and use ofsimple (i.e. substantially monochromatic) lens designs for substantiallymonochromatic optical illumination and image formation and detectionoperations.
 20. A laser illumination and imaging system, wherein specialmeasures are undertaken to ensure that (i) a minimum safe distance ismaintained between the VLDs in each PLIM and the user's eyes using alight shield, and (ii) the planar laser illumination beam is preventedfrom directly scattering into the FOV of the image formation anddetection module, from within the system housing.
 21. A laserillumination and imaging system, wherein the planar laser illuminationbeam and the field of view of the image formation and detection moduledo not overlap on any optical surface within the PLIIM system.
 22. Alaser illumination and imaging system, wherein the planar laserillumination beams are permitted to spatially overlap with the FOV ofthe imaging lens of the system only outside of the system housing,measured at a particular point beyond the light transmission window,through which the FOV is projected.
 23. A laser illumination andsubstantially-monochromatic imaging system, wherein the planar laserillumination arrays (PLIAs) and the image formation and detection (IFD)module are mounted in strict optical alignment on an optical bench suchthat there is no relative motion, caused by vibration or temperaturechanges, is permitted between the imaging lens within the IFD module andthe VLD/cylindrical lens assemblies within the PLIAs.
 24. A laserillumination and substantially-monochromatic imaging system, wherein theimaging module is realized as a photographic image recording module. 25.A laser illumination and substantially-monochromatic imaging system,wherein the imaging module is realized as an array of electronic imagedetection cells having short integration time settings for high-speedimage capture operations.
 26. A laser illumination andsubstantially-monochromatic imaging system, wherein a pair of planarlaser illumination arrays are mounted about an image formation anddetection module having a field of view, so as to produce asubstantially planar laser illumination beam which is coplanar with thefield of view during object illumination and imaging operations.
 27. Alaser illumination and monochromatic imaging system, wherein an imageformation and detection module projects a field of view through a firstlight transmission aperture formed in the system housing, and a pair ofplanar laser illumination arrays project a pair of planar laserillumination beams through second set of light transmission apertureswhich are optically isolated from the first light transmission apertureto prevent laser beam scattering within the housing of the system.
 28. Alaser illumination and substantially-monochromatic imaging system, theprinciple of Gaussian summation of light intensity distributions isemployed to produce a planar laser illumination beam having a powerdensity across the width the beam which is substantially the same forboth far and near fields of the system.
 29. A system for producingimages of objects by focusing a planar laser illumination beam withinthe field of view of an imaging lens so that the minimum width thereofalong its non-spreading direction occurs at the farthest object distanceof the imaging lens.
 30. A package dimensioning and identificationsystem contained in a single housing of compact construction, wherein aplanar laser illumination and monochromatic imaging subsystem isintegrated with a Laser Doppler Imaging and Profiling (LDIP) subsystemand contained within a single housing of compact construction.
 31. Apackage dimensioning and identification system, wherein the system ofclaim 1 projects a field of view through a first light transmissionaperture formed in the system housing, and a pair of planar laserillumination beams through second and third light transmission apertureswhich are optically isolated from the first light transmission apertureto prevent laser beam scattering within the housing of the system, andthe LDIP subsystem projects a pair of laser beams at different anglesthrough a fourth light transmission aperture.
 32. A packageidentification and measuring system, wherein an image-based scanningsubsystem is used to read bar codes on packages passing below or nearthe system, while a package dimensioning subsystem is used to captureinformation about the package prior to being identified.